Chapter 5.1, Problem 25ES

Let A denote the area between the graph of $f\left(x\right)=\sqrt{x}$ and the interval $\left[0,1\right]$ , and let $B$ denote the area between the graph of $f\left(x\right)=x^2$ and the interval $\left[0,1\right]$ , Explain geometrically why $A+B=1$ .