Help with math ? Alg.II?

Question

Solve (9x^4) + (7x^2) -2 =0 by factoring.

Answer 1

This is a quadratic in x^2
write y = x^2 to get

9y^2 + 7y - 2 = 0

Solve for y then solve for x

Answer 2

(9x^4) + (7x^2) -2 =0
(9x^2 - 2) (x^2 + 1) = 0
9x^2 = 2 or x^2 = -1
x = +/- (sqrt 2) / 3 {real, irrational roots}

or x = +/- i {imaginary root}

Answer 3

just substitute something like:

let z=x^2 then the equation becomes a quadratic:

9z^2+7z-2=0

(9z-2)(z+1)=0

so z=2/9 or z=-1

which means x^2=2/9 or x^2=-1, well x^2 can never be -1

so x^2 must be 2/9, so just take the square root of 2/9 to get

+/- sqrt(2)/3

Answer 4

answer is:

(9x^2 - 2) (x^2 + 1) = 0
check your work:

9^2 - 2
x^2 +1
-------------
9x^4 - 2x^2
........+ 9x^2 - 2
--------------------
9x^4 + 7x^2 - 2