Answer:

And on this case we can use the product rule for a derivate given by:

Where
and
And replacing we have this:

Step-by-step explanation:
We assume that the function of interest is:

And on this case we can use the product rule for a derivate given by:

Where
and
And replacing we have this:

Function since its passing the vertical line test
X = 15 , see photo for solutions
If r = 1/6 and 1/6 is next to 12, it's multiplication. so that's 12 x 1/6.
12 x 1/6 = 2 i believe.