Question

Which equation is not a quadratic equation?
y = 3x2 + 2
y = 5x - 2
y = -x2
y = 5x2 - 2x + 7

Answer 1

A quadratic equation is usually in the form:

$ax^{2} +bx +c$

where a, b and c are the coefficients of the expression and a ≠ 0. 

If a = 0, the equation becomes a linear expression and is no longer quadratic.

Hence, in the above options; y = 5x -2 is the only one that is not a quadratic equation.