CPM Homework Help : APCALC Problem 10-11

Multiple Choice: No calculator! A point of inflection for the curve $y = \frac { 12 } { x ^ { 2 } + 4 }$ is:

Compute without a calculator

Step 1:

$y^\prime=-12(x^2+4)^{-2}(2x)=-24x(x^2+4)^{-2}$

Step 2:

$y^{\prime\prime}=-24(x^2+4)^{-2}+48x(x^2+4)^{-3}(2x)$

Step 3:

Set $y^{\prime\prime} = 0$ and solve for $x$ .

Hint:

It may seem like there are two possible answers. Graph the function to check your results.