Question

Which equation is a quadratic equation?

y + 3 = −2x + 5 − 8x

y + 2x = −2x(4 − 3x) + 4

6x3 + y = (2x − 2)(3x + 7)

9x − y = (3x2 + 1)(5x − 1) + 4x

Answer 1

A quadratic must have an x squared. The first doesn't, the second will have when expanded, I think the third is a polynomial, I can't tell whether you mean x cubed or not. The last one will be a polynomial too.

4. x^2 - 8x - 20 = 0.
(x-10)(x+2)

Answer 2

so its B?