### Home > PC > Chapter 6 > Lesson 6.1.1 > Problem6-13

6-13.

Consider the function $f(x)=-\frac{1}{2}\left(x−1\right)^2+7$ for $1\le x\le4$.

1. Write the sum to find the area under the curve using left-hand endpoints and rectangles with widths of $1$. Since you are not using a calculator, be sure you set up your sum to include all of the factors. You do not need to actually calculate the sum.

$f(1)+f(2)+f(3)$

2. Write the sum using sigma notation.

$\displaystyle \sum_{k=1}^{3}(-\frac{1}{2}(??)^2 +7)$