From the graph you can see that:
- function is increasing (f'>0);
- then decreasing (f'<0);
- then again increasing (f'>0);
- again decreasing (f'<0);
- at last increasing (f'>0).
This gives you 4 turning points, where the derivative changes the sign: 2 maxima (f increasing and then decreasing) and 2 minima (f decreasing and then increasing).
Answer: true.
