Why is this problem maximum -x^2+2x+4

Here is another math questions. i will keep asking different questions. 4^2x=6

One side of a rectangle is 7 centimeters shorter than six times the other side. find the length of the longer side if we also know that the perimeter of the rectangle is 266 centimeters.

Ablue whale traveled 3112 miles in 214hours. what was the whale's rate in yards per hour? (1 mile = 1,760 yards)