# Thread: interval and concave downward question

1. ## interval and concave downward question

y = 8x^3 - 2x^4
find intervals of the graph when it concaves downward.

(negative infinity, 0) ( 2, positive infinity)
am i correct?

2. It's concave downwards if $y''<0$ and $y''(x)=24(x^2-2x)=24x(x-2)$ so...yeah you're right.