Question

Which of the following equations represents a quadratic function?

y(y + 4)(y - 6) = 0
z2 + 2 = 3z(z2 - 1)
(2x - 3)(4x + 5) = 10x
(3b)(5b – 7)(b + 8) = 0

Answer 1

A quadratic equation is one in which the highest exponent of a variable is 2. We can solve this problem by expanding each choices then find which has highest exponent equal to 2.

y(y + 4)(y - 6) = 0 ---> By expansion we get y^3, therefore highest exponent is 3.

z2 + 2 = 3z(z2 - 1) ---> By expansion we get z^3, therefore highest exponent is 3.

(2x - 3)(4x + 5) = 10x ---> By expansion we get x^2, therefore highest exponent is 2.

(3b)(5b – 7)(b + 8) = 0 ---> By expansion we get b^3, therefore highest exponent is 3.

The answer to this problem is therefore:

(2x - 3)(4x + 5) = 10x