Explanation:
It asks you to choose values for w, the width, and evaluate the equation for each. It describes the constraint "the perimeter of 20 units" The perimeter of a rectangle is the length of all the lines of a regtangle.
Or
2L + 2W = 20 reduce this to simplest for by dividing both sides by 2;
L + W = 10, so the length plus the width is 10. Rearrange it to be W = 10 - L. Values of W can range from 1 to 9. Now sove for a few points in the function.
f(W) = 10W - W^2
3; 10(3) - 3^2 = 30 - 9 = 21.
If we look at the constraint, L = 10 - W, when the width is 3 the length must be 7. The area of a rectangle is L x W, 3 x 7 = 21. That checks against the function.
Solve for additional points.
4; 10(4) - 4^2 = 40 - 16 = 24.
If W is 4 the L is 6 and 4 x 6 = 24