How can I solve this absolute value equation?
$begingroup$
This is the equation:
$|sqrt{x-1} - 2| + |sqrt{x-1} - 3| = 1$
Any help would be appreciated. Thanks!
algebra-precalculus radicals absolute-value
New contributor
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add a comment |
$begingroup$
This is the equation:
$|sqrt{x-1} - 2| + |sqrt{x-1} - 3| = 1$
Any help would be appreciated. Thanks!
algebra-precalculus radicals absolute-value
New contributor
$endgroup$
1
$begingroup$
What did you try? For example, transfer one of the terms on the left to the right and then square both sides.
$endgroup$
– астон вілла олоф мэллбэрг
2 days ago
add a comment |
$begingroup$
This is the equation:
$|sqrt{x-1} - 2| + |sqrt{x-1} - 3| = 1$
Any help would be appreciated. Thanks!
algebra-precalculus radicals absolute-value
New contributor
$endgroup$
This is the equation:
$|sqrt{x-1} - 2| + |sqrt{x-1} - 3| = 1$
Any help would be appreciated. Thanks!
algebra-precalculus radicals absolute-value
algebra-precalculus radicals absolute-value
New contributor
New contributor
New contributor
asked 2 days ago
Jill and JillJill and Jill
303
303
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New contributor
1
$begingroup$
What did you try? For example, transfer one of the terms on the left to the right and then square both sides.
$endgroup$
– астон вілла олоф мэллбэрг
2 days ago
add a comment |
1
$begingroup$
What did you try? For example, transfer one of the terms on the left to the right and then square both sides.
$endgroup$
– астон вілла олоф мэллбэрг
2 days ago
1
1
$begingroup$
What did you try? For example, transfer one of the terms on the left to the right and then square both sides.
$endgroup$
– астон вілла олоф мэллбэрг
2 days ago
$begingroup$
What did you try? For example, transfer one of the terms on the left to the right and then square both sides.
$endgroup$
– астон вілла олоф мэллбэрг
2 days ago
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
Let $a =sqrt{x-1}$,
$|a-2|+|a-3|=1$
Check for solutions in the different regions for $a$.
Region 1: $a<2$.
Then we have $(2-a)+(3-a)=1$, i.e. $5-2a=1$, so that $a=2$.
Region 2: $2leq aleq 3$. We have $(a-2)+(3-a)=1$. This is true for every such $a$.
Final region 3: $3<a$. We have $(a-2)+(a-3)=1$ so that $a=3$.
In summary, $2 leq sqrt{x-1} leq 3$.
Thus $5 leq x leq 10$.
$endgroup$
$begingroup$
I think you have the equation wrong. There should be a one on the right side not a three.
$endgroup$
– Shervin Sorouri
2 days ago
1
$begingroup$
yeah it's being sorted
$endgroup$
– George Dewhirst
2 days ago
$begingroup$
For region $(1)$ we must have $(2-a)+(3-a) = 1.$ Same for region $(2)$.
$endgroup$
– Dbchatto67
2 days ago
add a comment |
$begingroup$
Let $x$ be a solution of the equation. Notice $x geq 1$, since $sqrt{x-1}$ has its domain as $x geq 1$.
If $x geq 10$, then each of the absolute value is just the term inside (i.e.$|sqrt{x-1}-2| = sqrt{x-1}-2$ and similarly $|sqrt{x-1}-3| =sqrt{x-1}-3$) so that the given equation in this case becomes $2sqrt{x-1}-5=1$. Solve for $x$ you get $x=10$. Thus we have shown that IF there is a solution that is greater than or equal to $10$ then $x$ must be $10$; we have not yet proven that $10$ is a solution. However, we can check that $x=10$ is a solution by plugging it back in.
If $10 > x geq 5$ then $|sqrt{x-1}-2| = sqrt{x-1}-2$ and $|sqrt{x-1}-3| =-sqrt{x-1}+3$ so that the given equation becomes (after simplification) $1=1$; this does not give us a new information, but we can check that any number $x$ such that $10 > x geq 5$ satisfies the original equation.
If $5 > x geq 1$ then $|sqrt{x-1}-2| = -sqrt{x-1}+2$ and $|sqrt{x-1}-3| = -sqrt{x-1}+3$, so that the given equation becomes (after simplification) $sqrt{x-1}=2$, implying $x=5$, contradicting our assumption that $5 > x$. Thus, there cannot be any solution in this case.
Hence, the solution are $5 leq x leq 10$.
In general, any time you see an absolute value in a given equation, it's a good idea to divide into cases according to whether each expression in an absolute value is negative or non-negative.
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2 Answers
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2 Answers
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$begingroup$
Let $a =sqrt{x-1}$,
$|a-2|+|a-3|=1$
Check for solutions in the different regions for $a$.
Region 1: $a<2$.
Then we have $(2-a)+(3-a)=1$, i.e. $5-2a=1$, so that $a=2$.
Region 2: $2leq aleq 3$. We have $(a-2)+(3-a)=1$. This is true for every such $a$.
Final region 3: $3<a$. We have $(a-2)+(a-3)=1$ so that $a=3$.
In summary, $2 leq sqrt{x-1} leq 3$.
Thus $5 leq x leq 10$.
$endgroup$
$begingroup$
I think you have the equation wrong. There should be a one on the right side not a three.
$endgroup$
– Shervin Sorouri
2 days ago
1
$begingroup$
yeah it's being sorted
$endgroup$
– George Dewhirst
2 days ago
$begingroup$
For region $(1)$ we must have $(2-a)+(3-a) = 1.$ Same for region $(2)$.
$endgroup$
– Dbchatto67
2 days ago
add a comment |
$begingroup$
Let $a =sqrt{x-1}$,
$|a-2|+|a-3|=1$
Check for solutions in the different regions for $a$.
Region 1: $a<2$.
Then we have $(2-a)+(3-a)=1$, i.e. $5-2a=1$, so that $a=2$.
Region 2: $2leq aleq 3$. We have $(a-2)+(3-a)=1$. This is true for every such $a$.
Final region 3: $3<a$. We have $(a-2)+(a-3)=1$ so that $a=3$.
In summary, $2 leq sqrt{x-1} leq 3$.
Thus $5 leq x leq 10$.
$endgroup$
$begingroup$
I think you have the equation wrong. There should be a one on the right side not a three.
$endgroup$
– Shervin Sorouri
2 days ago
1
$begingroup$
yeah it's being sorted
$endgroup$
– George Dewhirst
2 days ago
$begingroup$
For region $(1)$ we must have $(2-a)+(3-a) = 1.$ Same for region $(2)$.
$endgroup$
– Dbchatto67
2 days ago
add a comment |
$begingroup$
Let $a =sqrt{x-1}$,
$|a-2|+|a-3|=1$
Check for solutions in the different regions for $a$.
Region 1: $a<2$.
Then we have $(2-a)+(3-a)=1$, i.e. $5-2a=1$, so that $a=2$.
Region 2: $2leq aleq 3$. We have $(a-2)+(3-a)=1$. This is true for every such $a$.
Final region 3: $3<a$. We have $(a-2)+(a-3)=1$ so that $a=3$.
In summary, $2 leq sqrt{x-1} leq 3$.
Thus $5 leq x leq 10$.
$endgroup$
Let $a =sqrt{x-1}$,
$|a-2|+|a-3|=1$
Check for solutions in the different regions for $a$.
Region 1: $a<2$.
Then we have $(2-a)+(3-a)=1$, i.e. $5-2a=1$, so that $a=2$.
Region 2: $2leq aleq 3$. We have $(a-2)+(3-a)=1$. This is true for every such $a$.
Final region 3: $3<a$. We have $(a-2)+(a-3)=1$ so that $a=3$.
In summary, $2 leq sqrt{x-1} leq 3$.
Thus $5 leq x leq 10$.
edited 2 days ago
answered 2 days ago
George DewhirstGeorge Dewhirst
7514
7514
$begingroup$
I think you have the equation wrong. There should be a one on the right side not a three.
$endgroup$
– Shervin Sorouri
2 days ago
1
$begingroup$
yeah it's being sorted
$endgroup$
– George Dewhirst
2 days ago
$begingroup$
For region $(1)$ we must have $(2-a)+(3-a) = 1.$ Same for region $(2)$.
$endgroup$
– Dbchatto67
2 days ago
add a comment |
$begingroup$
I think you have the equation wrong. There should be a one on the right side not a three.
$endgroup$
– Shervin Sorouri
2 days ago
1
$begingroup$
yeah it's being sorted
$endgroup$
– George Dewhirst
2 days ago
$begingroup$
For region $(1)$ we must have $(2-a)+(3-a) = 1.$ Same for region $(2)$.
$endgroup$
– Dbchatto67
2 days ago
$begingroup$
I think you have the equation wrong. There should be a one on the right side not a three.
$endgroup$
– Shervin Sorouri
2 days ago
$begingroup$
I think you have the equation wrong. There should be a one on the right side not a three.
$endgroup$
– Shervin Sorouri
2 days ago
1
1
$begingroup$
yeah it's being sorted
$endgroup$
– George Dewhirst
2 days ago
$begingroup$
yeah it's being sorted
$endgroup$
– George Dewhirst
2 days ago
$begingroup$
For region $(1)$ we must have $(2-a)+(3-a) = 1.$ Same for region $(2)$.
$endgroup$
– Dbchatto67
2 days ago
$begingroup$
For region $(1)$ we must have $(2-a)+(3-a) = 1.$ Same for region $(2)$.
$endgroup$
– Dbchatto67
2 days ago
add a comment |
$begingroup$
Let $x$ be a solution of the equation. Notice $x geq 1$, since $sqrt{x-1}$ has its domain as $x geq 1$.
If $x geq 10$, then each of the absolute value is just the term inside (i.e.$|sqrt{x-1}-2| = sqrt{x-1}-2$ and similarly $|sqrt{x-1}-3| =sqrt{x-1}-3$) so that the given equation in this case becomes $2sqrt{x-1}-5=1$. Solve for $x$ you get $x=10$. Thus we have shown that IF there is a solution that is greater than or equal to $10$ then $x$ must be $10$; we have not yet proven that $10$ is a solution. However, we can check that $x=10$ is a solution by plugging it back in.
If $10 > x geq 5$ then $|sqrt{x-1}-2| = sqrt{x-1}-2$ and $|sqrt{x-1}-3| =-sqrt{x-1}+3$ so that the given equation becomes (after simplification) $1=1$; this does not give us a new information, but we can check that any number $x$ such that $10 > x geq 5$ satisfies the original equation.
If $5 > x geq 1$ then $|sqrt{x-1}-2| = -sqrt{x-1}+2$ and $|sqrt{x-1}-3| = -sqrt{x-1}+3$, so that the given equation becomes (after simplification) $sqrt{x-1}=2$, implying $x=5$, contradicting our assumption that $5 > x$. Thus, there cannot be any solution in this case.
Hence, the solution are $5 leq x leq 10$.
In general, any time you see an absolute value in a given equation, it's a good idea to divide into cases according to whether each expression in an absolute value is negative or non-negative.
$endgroup$
add a comment |
$begingroup$
Let $x$ be a solution of the equation. Notice $x geq 1$, since $sqrt{x-1}$ has its domain as $x geq 1$.
If $x geq 10$, then each of the absolute value is just the term inside (i.e.$|sqrt{x-1}-2| = sqrt{x-1}-2$ and similarly $|sqrt{x-1}-3| =sqrt{x-1}-3$) so that the given equation in this case becomes $2sqrt{x-1}-5=1$. Solve for $x$ you get $x=10$. Thus we have shown that IF there is a solution that is greater than or equal to $10$ then $x$ must be $10$; we have not yet proven that $10$ is a solution. However, we can check that $x=10$ is a solution by plugging it back in.
If $10 > x geq 5$ then $|sqrt{x-1}-2| = sqrt{x-1}-2$ and $|sqrt{x-1}-3| =-sqrt{x-1}+3$ so that the given equation becomes (after simplification) $1=1$; this does not give us a new information, but we can check that any number $x$ such that $10 > x geq 5$ satisfies the original equation.
If $5 > x geq 1$ then $|sqrt{x-1}-2| = -sqrt{x-1}+2$ and $|sqrt{x-1}-3| = -sqrt{x-1}+3$, so that the given equation becomes (after simplification) $sqrt{x-1}=2$, implying $x=5$, contradicting our assumption that $5 > x$. Thus, there cannot be any solution in this case.
Hence, the solution are $5 leq x leq 10$.
In general, any time you see an absolute value in a given equation, it's a good idea to divide into cases according to whether each expression in an absolute value is negative or non-negative.
$endgroup$
add a comment |
$begingroup$
Let $x$ be a solution of the equation. Notice $x geq 1$, since $sqrt{x-1}$ has its domain as $x geq 1$.
If $x geq 10$, then each of the absolute value is just the term inside (i.e.$|sqrt{x-1}-2| = sqrt{x-1}-2$ and similarly $|sqrt{x-1}-3| =sqrt{x-1}-3$) so that the given equation in this case becomes $2sqrt{x-1}-5=1$. Solve for $x$ you get $x=10$. Thus we have shown that IF there is a solution that is greater than or equal to $10$ then $x$ must be $10$; we have not yet proven that $10$ is a solution. However, we can check that $x=10$ is a solution by plugging it back in.
If $10 > x geq 5$ then $|sqrt{x-1}-2| = sqrt{x-1}-2$ and $|sqrt{x-1}-3| =-sqrt{x-1}+3$ so that the given equation becomes (after simplification) $1=1$; this does not give us a new information, but we can check that any number $x$ such that $10 > x geq 5$ satisfies the original equation.
If $5 > x geq 1$ then $|sqrt{x-1}-2| = -sqrt{x-1}+2$ and $|sqrt{x-1}-3| = -sqrt{x-1}+3$, so that the given equation becomes (after simplification) $sqrt{x-1}=2$, implying $x=5$, contradicting our assumption that $5 > x$. Thus, there cannot be any solution in this case.
Hence, the solution are $5 leq x leq 10$.
In general, any time you see an absolute value in a given equation, it's a good idea to divide into cases according to whether each expression in an absolute value is negative or non-negative.
$endgroup$
Let $x$ be a solution of the equation. Notice $x geq 1$, since $sqrt{x-1}$ has its domain as $x geq 1$.
If $x geq 10$, then each of the absolute value is just the term inside (i.e.$|sqrt{x-1}-2| = sqrt{x-1}-2$ and similarly $|sqrt{x-1}-3| =sqrt{x-1}-3$) so that the given equation in this case becomes $2sqrt{x-1}-5=1$. Solve for $x$ you get $x=10$. Thus we have shown that IF there is a solution that is greater than or equal to $10$ then $x$ must be $10$; we have not yet proven that $10$ is a solution. However, we can check that $x=10$ is a solution by plugging it back in.
If $10 > x geq 5$ then $|sqrt{x-1}-2| = sqrt{x-1}-2$ and $|sqrt{x-1}-3| =-sqrt{x-1}+3$ so that the given equation becomes (after simplification) $1=1$; this does not give us a new information, but we can check that any number $x$ such that $10 > x geq 5$ satisfies the original equation.
If $5 > x geq 1$ then $|sqrt{x-1}-2| = -sqrt{x-1}+2$ and $|sqrt{x-1}-3| = -sqrt{x-1}+3$, so that the given equation becomes (after simplification) $sqrt{x-1}=2$, implying $x=5$, contradicting our assumption that $5 > x$. Thus, there cannot be any solution in this case.
Hence, the solution are $5 leq x leq 10$.
In general, any time you see an absolute value in a given equation, it's a good idea to divide into cases according to whether each expression in an absolute value is negative or non-negative.
answered 2 days ago
Cute BrownieCute Brownie
1,085417
1,085417
add a comment |
add a comment |
Jill and Jill is a new contributor. Be nice, and check out our Code of Conduct.
Jill and Jill is a new contributor. Be nice, and check out our Code of Conduct.
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1
$begingroup$
What did you try? For example, transfer one of the terms on the left to the right and then square both sides.
$endgroup$
– астон вілла олоф мэллбэрг
2 days ago