Question

Which equation is a quadratic equation?
Answer
5x + y = -2(x + 5)
3x^3 - y = (3x - 2)(x + 5)
y + 7x = -3x(7 - 2x) + 11
y - 9 = (x^2 + 1)(5x - 1) + 3

Answer 1

third one

Answer 2

a quadratic equation has degree 2 - that is it will contain x^2 as the highest power

Answer 3

yes third one is correct
if you expand the brackets you get 6x^2 as term with the highest power