Which equation is a quadratic equation?

y = 2x(5 − x) + 7x

y = 8x + 2

y + x2 = (x − 2)(x + 8)

y − 7x = (x2 + 1)(x − 3)

Question

Which equation is a quadratic equation?

 y = 2x(5 − x) + 7x

 y = 8x + 2

 y + x2 = (x − 2)(x + 8)

 y − 7x = (x2 + 1)(x − 3)

anonymous · Answer

which one has only x^2 terms and below

anonymous · Answer

C?

anonymous · Answer

actually this question is a bit tricky since the third one looks quadratic, but actually is not

anonymous · Answer

$$y + x^2 = (x − 2)(x + 8) $$
$$y+x^2=x^2+6x-16$$ and the $x^2$ term cancels from both sides to give 
$$y=6x-16$$ so it is not quadratic

anonymous · Answer

:/

anonymous · Answer

multiply out for the first one, combine like terms, and you will see that it is a quadratic

anonymous · Answer

oh yea, duh! I should've seen that. Thank you

anonymous · Answer

yw