Question

f(x)=x^4+x^2-2 On which interval is f increasing?
A. (-1/√2, infinity )
B. (-1/√2 , 1/√2)
C. (0, infinity)
D. (-infinity, 0)
E. (-infinity, -1/√2)

Answer 1

take the derivative set it equal to zero, find intervals where is is positive and negative

Answer 2

i got x=0 and x= -1/√ 2 as critical points but i think thats wrong...

Answer 3

you missed a zero

Answer 4

oops it is a plus sign!~

Answer 5

so i was wrong?

Answer 6

\[f'(x)=4x^3+2x=2x(x^2+1)\]

Answer 7

\(x^2+1\) is never zero as \(x^2\geq 0\) always,so the only zero is at \(x=0\)

Answer 8

ohh ok thanks.