Question

What are the solutions of the equation x^4-9x^2+8=0? Use u substitution to solve.

Answer 1

Answer:

The answer is the second option

Step-by-step explanation:

Let u=x^2.

$( {x}^{2} ) {}^{2} - 9( {x}^{2} ) + 8( {x}^{2} ) {}^{0}$

${u}^{2} - 9u + 8$

$(u - 1)(u - 8)$

$u = 1$

$u = 8$

Set this equal to x^2

${x}^{2} = 1$

$x = 1$

or

$x = - 1$

${x}^{2} = 8$

$x = 2 \sqrt{2}$

or

$x = - 2 \sqrt{2}$