Question

Which equation is a quadratic equation?

5x + y = −2(x + 5)

3x3 − y = (3x − 2)(x + 5)

y + 7x = −3x(7 − 2x) + 11

y − 9 = (x2 + 1)(5x − 1) + 3

Answer 1

Hint: Isolate y

Answer 2

i did it for the first one but for all the other ones its complicated

Answer 3

Quadratic means that your highest exponent would be 2. So the best way to solve is to expand them, and see which one gives you 2 as the highest exponent

Answer 4

Well, you can automatically eliminate the second one because it has an x^3 term in it.

Answer 5

ok

Answer 6

You can really do this without pen and paper if you look closely enough

Answer 7

The first option would not even produce a quadratic because you wont ever end up multiplying x times x to get x^2

Answer 8

i think its the fourth option

Answer 9

For the fourth option, you have an x^2 term that will eventually be multiplied by x to produce an x^3 term, so it can't be that one either.

Answer 10

but it wouldnt be the third option either due to the fact that you will be multiplying by three terms with the variable x

Answer 11

You should actually try multiplying it out and isolating y to see what happens. I am assuming you know how to multiply.

Answer 12

of course

Answer 13

oh so it is the third one