The name Quadratic comes from "quad" meaning square, because the variable gets squared (like x2). However, it is important to not that an expression is only quadratic if and only if the highest degree of a term is 2. Therefore, the quadratic equations from the pool of choices would be as follows:
3x^2 + 5x - 7 = 0
5x^2+ 15x = 0
x^2 - 4x = 4x + 7
