Let $a$ and $b$ be real numbers, where $a < b$, and let $A = (a,a^2)$ and $B = (b,b^2)$. The line $\overline{AB}$ (meaning the unique line that contains the point $A$ and the point $B$) has slope $2$. Find $a + b$.
Slope = (a^2 - b^2) / ( a -b) = [ (a + b) (a -b) ] / (a -b) = 2 → a + b = 2
+448 
