Need help finding formula and area​

The $x$-intercepts of the parabola $y = x^2 + bx + c$ are $(-3,0)$ and $(5,0).$ find the equation of the parabola, and submit your answer in $y = ax^2 + bx + c$ form.

Barney & noblet customers can choose to purchase a membership for $25 per year members receive 10% off all store purchases 1. how much would a member pay per year if he bought $50 worth of items each year? 2. write a slope-intercept equation that expresses how much a member pays per year using x to represent his purchases per year 3. how much would a member have to spend per year to pay off his membership fee?

Two florida panthers were weighed. one weighs 6x+21 pounds and the two together weigh 14x+11 pounds how much does he other panther weigh alone