Question

Quadratic Formula to solve this
x^4-12x^2-64=0

Answer 1

@annas Do you know how to do this?

Answer 2

Let x^2 = y
then
y^2 - 12y - 64 = 0

you can solve this by factoring - no need to use the quadratic formula

Answer 3

I have to use the quadratic formula if I want the credit. I know how to use the quadratic formula but since this isn't in the right form I can't.

Answer 4

(y - 16)(y + 4) = 0
y =16 or -4
thus
x^2 = 16 or -4
if we only need real solution we can ignore -4

so we are left with x^2 = 16

Answer 5

oh ok
useing quadratic formula
y = -(-12) +/- sqrt((-12)^2 - 4*1*-64) / 2
= [12 +/- sqrt(144+256)] / 2
= [12 +/- sqrt400] / 2
= 6 + 10 or 6 - 10
= 16 or -4

now since y = x^2

x^2 = 16

Answer 6

So x=-4, 4
or x=-2i or 2i

Answer 7

yes