Question

Find all real zeros of y=x^4 - 40x^2 + 144

Answer 1

let x^2 = X
solve X^3 - 40X + 144 = 0

Answer 2

then 2 values of X give x = +/- sqrtX

Answer 3

* thats X^2 not X^3

Answer 4

you can solve X^2 - 40X + 144 = 0 by factoring

Answer 5

can you solve that equation? do you need help?

Answer 6

I came up with x=+-2 and x=+-6 are those correct?

Answer 7

yes