Question

Which equation is a quadratic equation?
Answer







y + 3 = 5x + 10








y + 4x2 = (4x - 2)(x + 3)








y - 8x = (x2 + 1)(9x - 7)








y = 2x + 7x(x + 1)

Answer 1

quadratic equations are equations where the highest power of x is 2 , so anything with x^3 in it is not a quadratic. multiply all the brackets out and look for the highest power of x

Answer 2

is it the 4th one?

Answer 3

ill go through them one at a time, just a sec

Answer 4

y + 3 = 5x + 10

well the highest power of x here is 1 , because all we have is an x . this is not a quadratic, and its known as a "linear" equation (because it's a straight line on a graph)

Answer 5

y + 4x^2 = (4x - 2)(x + 3)

y + 4x^2 = 4x^2 + 10x -6

now the 4x^2 terms cancel
leaving y = 10x + 6

another linear

Answer 6

y - 8x = (x2 + 1)(9x - 7)

y - 8x = 9x^3 -7x^2 +9x - 7

a cubic!

Answer 7

finally:

y = 2x + 7x(x + 1)

y= 2x + 7x^2 +7x

the highest power of x is 2 so we have a quadratic like you suggested :D