How do you prove a triangle is a right triangle with coordinates?

I'm at a bookstore with $\$35$ in my pocket and a $20\%$-off coupon. what is the cost of the most expensive book i can buy with my money and the coupon? (assume that there are books of every possible price in the bookstore. it's a large bookstore! )

The height of a plant, in inches, p years after planting it is given by the polynomial function r(p) = -2p% + 270p. find the height of the plant when p = 90 years.

Ataxi company charges $3 for pick-up plus $0.65 for each mile. select the expressions that represent the cost in dollars for a taxi pick-up and m miles. mark all that apply.