a quadratic equation is an equation with a degree of 2.
well, is not 2x + x + 3 for sure, and is not 3x³ + 2x + 2 either, that one is a cubic, 3rd degree.
well, one would think is 0x² - 4x + 7, however 0x² is really 0, anything times 0 is 0, so the deceptive equation is really -4x + 7, which is not a quadratic.
5x² - 4x + 5 on the other hand is.