Question

Which function is a quadratic function? a(x) = –2x^3 + 2x – 6 b(x) = 5x^3 + 8x^2 + 3 c(x) = –8x^2 + 3x – 5 d(x) = 6x^4 + 2x – 3

Answer 1

c(x) = –8x^2 + 3x – 5 is a quadratic

Explanation:

A quadratic function involves the 2nd power of x: x^2, and may (or may not) involve the 1st and zeroth power of x.

a(x) = -2x^3 is not a quadratic because of that exponent 3; in a quadratic, the highest power is always 2.

b(x) = 5x^3 + 8x^2 + 3 is not a quadratic for the same reason that a(x) is not a quadratic.

c(x) = –8x^2 + 3x – 5 is a quadratic: the highest power of x is x^2, the other powers are x^1 and x^0.