Question

Which of the following is not a quadratic equation?

Answer 1

D is not a quadratic equation because the x² disappears while calculating.

Answer 2

For this case we must indicate which of the equations is not quadratic.

A quadratic equation is of the form:

$ax ^ 2 + bx + c = 0$

It is grade 2, the greatest exponent is 2.

So, we have:

Option A:

$ax ^ 2 + bx = 0$

It is a quadratic equation.

Option B:

$3x ^ 2 = -4x-1$

Rewritten:

$3x ^ 2 + 4x + 1 = 0$

It is a quadratic equation.

Option C:

$x ^ 2 = 5\\x ^ 2-5 = 0$

It is a quadratic equation

Option D:

$x ^ 2 + 3x-2 = x ^ 2-2x$

It can be rewritten as:

$x ^ 2 + 3x-2-x ^ 2 + 2x = 0\\5x-2 = 0$

It is not grade 2, it is not a quadratic equation.

Answer:

Option D