Is f(x)=3/x-2x concave or convex at x=9/4?
1 Answer
Feb 14, 2016
Convex
Explanation:
Find the value of the second derivative at
To find the function's second derivative, recall that
f(x)=3x^-1-2x
f'(x)=-3x^-2-2
f''(x)=6x^-3=6/x^3
The value of the second derivative at
f''(9/4)=6/(9/4)^3
This could be simplified, but it is evidently positive. Thus the function is convex at