Question

Find all zeroes for f(x)=x^4-3x^2-4

Answer 1

Zeros, sorry!

Answer 2

Use a substitution, u = x^2, then u^4 = x^2
x^4 - 3x^2 - 4 = 0
Apply substitution:
u^2 - 3u - 4 = 0
Now factor it the normal way:
(u -4)(u + 1) = 0
u - 4 = 0 or u + 1 = 0
u = 4 or u = -1
But since u = x^2,
x^2 = 4 or x^2 = -1
x = +-2 or x = +-i

Answer 3

@mathstudent55 thank you so much!!! That really helped a lot :) I was taught a more confusing way, but I love this new method. Thanks!

Answer 4

@mathstudent55 thank you so much!!! That really helped a lot :) I was taught a more confusing way, but I love this new method. Thanks!

Answer 5

You're very welcome!