How do i decide theese curves?

The value of f' at x = 2 = slope of the curve at that point....

slope of tangent line 1 =  4/2     slope of line 2 = - 1/3

slope 1 * slope 2 = -4/6 = -2/3  

Now see this is a math question.  No need for the off-topic flag here.

In both diagrams, the tangent line is given. By definition of derivative, the derivatives of the functions at the point of tangency is just the slope of tangent line.

Therefore, by calculating(or approximating? :D) the slope of the tangents, we get \(p'(2) = 2\) and \(q'(2) = \dfrac{-1}{3}\).

And then, we see the graph of p(x) passes through (2,3), and the graph of q(x) passes through (2, -1). So p(2) = 3 and q(2) = -1.

By product rule of differentiation:

\(\quad r'(2)\\ = p(2) q'(2) + q(2) p'(2)\\ = 3\cdot \dfrac{-1}{3} + (-1)\cdot 2\\ = -1 - 2\\ = -3\)

There we go :)