What is a discriminant and what’s the formula, if there is one?

Aheated piece of metal cools according to the function c(x) = (.5)x ? 7, where x is measured in hours. a device is added that aids in cooling according to the function h(x) = ? x ? 2. what will be the temperature of the metal after two hours?

If i have one apple and give you the apple, how many apples do i have?

What expression is equivalent to 42x-56y