Factor and solve for x

Question

1) x^4 - 9x^2> 0

2) 4x2^x - x^3 2^x<or equal to 0

I don't know where to start on 1 but for 2 I got
X<or equal to -4 or x> or equal to 4

Could some one please explain how to do 1 and tell me if I did 2 correctly?

Answer 1

1)x^2(x^2-9)=x^2(x-3)(x+3)>0
x>3 or x<-3

2)x*2^x(4-x^2)=x*2^x(2-x)(2+x)<=0
-2<=x<=0 or x>=2

Answer 2

How did you get those 2 answers for 2?

Answer 3

a^2-b^2=(a-b)(a+b)
4-x^2=2^2-x^2