Question

Which equation is a quadratic equation?

3x − y = 8x + 2

y = 7x(5 − 2x) + 9

7x2 + y = (3 + x)(7x − 1)

y − 3 = (x2 − 3)(8x + 3)

Answer 1

A quadratic equation has an x^2 term in it. The x^2 term is the largest exponent.

3x - y = 8x + 2
-y = -3x + 8x + 2
-y = 5x + 2
y = -5x - 2

This is not a quadratic equation.

Answer 2

y = 7x(5 - 2x) + 9
y = 35x - 14x^2 + 9
y = -14x^2 + 35x + 9

This is a quadratic equation.

Answer 3

7x^2 + y = (3 + x)(7x - 1)
7x^2 + y = 21x - 3 + 7x^2 - x
7x^2 + y = 20x - 3 + 7x^2
y = 20x - 3 + 7x^2 - 7x^2
y = 20x - 3

Even though this equation looks like it has an x^2 term, after solving for y, you can see that it is not a quadratic equation.

Answer 4

No you try the last one.

Answer 5

*Now

Answer 6

@Aaron0620, Do you know how to solve for y in the last equation?

Answer 7

urgg fine i will lol, and yes ill try

Answer 8

Start by multiplying the two binomials together.

Answer 9

7x^2 + y = (3 + x)(7x − 1)
-7x^2 -7x^2
--------------------------
y= -7x^2+20x -3
is that right?

Answer 10

7x^2 + y = 21x - 3 + 7x^2 - x
7x^2 + y = 20x + 7x^2 - 3
y = 20x + 7x^2 - 3 - 7x^2
y = 20x - 3

You are close, but the 7x^2's cancel each other out. So even though it looks like there is an x^2 term in the beginning, after you solve for y, you can see that it is not a quadratic equation.

The only quadratic equation is #2.
You are welcome. :)

Answer 11

alright thank you!

Answer 12

No problem. c: