Solve -x^4+4x^2 <0

Question

Solve it please solve it

Answer 1

-x^4 + 4x^2 < 0

x^4 - 4x^2 > 0

x^2(x^2 - 4) > 0

x^2(x-2)(x+2) > 0

i.e. (x-2)(x+2) > 0   since x^2 always greater than zero.

so, (x-2) and (x+2) both negative, gives x < -2

or, (x-2) and (x+2) both positive, gives x > 2

Two solutions: x < -2, x > 2