If f(x) = 2x2 + 3, then which of the following represent f(-1)?

What is the answer to this question? i'm a bit stumped. also how do i do it? 5(x - 4) = 2(x + 5)

The volume of gas a balloon can hold varies directly as the cube of its radius. imagine a balloon with a radius of 3 inches can hold 81 cubic inches of gas. how many cubic inches of gas must be released to reduce the radius down to 2 inches?

Solve each quadratic equation by factoring and using the zero product property. x^2 - 8x + 30 = 3x