# Thread: solve the equation by an appropriate substitution

1. ## solve the equation by an appropriate substitution

solve the equation by making an appropriate substitution

x^4 - 5x^2 + 4 = 0

any help in explaining what needs to be done to solve this question will be appreciated. what substitution are they talking about to be more precise on whats confusing me about this question. (should i just substitute random values for x until i find a solution?)

2. Originally Posted by netlab
solve the equation by making an appropriate substitution

x^4 - 5x^2 + 4 = 0

any help in explaining what needs to be done to solve this question will be appreciated. what substitution are they talking about to be more precise on whats confusing me about this question. (should i just substitute random values for x until i find a solution?)
If you let $\displaystyle y = x^2$, then the equation becomes:

$\displaystyle y^2 - 5y + 4 =0$

Which is a quadratic. Can you solve those?

3. ok thanks a lot that clears up a lot, and yes i can solve quadratic equations

4. Originally Posted by netlab
ok thanks a lot that clears up a lot, and yes i can solve quadratic equations
No problem.

Just remember that once you have solved for y, you must change the variable back to the original and solve for x!

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### equation by any appropriate substitution

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