"Linear" means that the largest exponent of x after the right side is multiplied out and all like terms collected is 1. "Quadratic" means that the largest exponent of x after the right side is multiplied out and all like terms collected is 2. "Cubic" means that the largest exponent of x after the right side is multiplied out and all like terms collected is 3. "Quartic" means that the largest exponent of x after the right side is multiplied out and all like terms collected is 4. "Quintic" means that the largest exponent of x after the right side is multiplied out and all like terms collected is 5. But right now you're only studying the first two, "linear" and "quadratic" --------------------------------------------------------------That doesn't need to be multiplied out or any terms collected. And the largest power of x is 1, so it's linear. ------------------------------- That needs to be multiplied out and like terms collected: Use FOIL to multiply it out: Collect like terms: The largest power of x is 2, so it's quadratic. [Note: You probably could just have looked at it and seen that the largest power of x would end up being be 2 if you multiplied it out and collected like terms without actually bothering to to do so.] Edwin