Looking for the area of the curved part​

What constants do you need to add to each of the following quadratic equations to complete the square? 2x2 - 3x = 0 x2 - 8x = 0 2x2 - 11x = 18

Mr. thompson is on a diet. he currently weighs 260 pounds. he loses 4 pounds per month. what part of the story makes the relationship not proportional?

Having a hard time understanding this question (see attachment).