Question

Which equation is a quadratic equation?

5x − 2 = y

y + 15x2 = (3x − 2)(5x + 7)

y = 3x(5 − x) + 7

y + 2 = (3x2 + 10)(x − 1)

Answer 1

Are there any that you can eliminate right from the beginning?

Answer 2

maybe...
5x − 2 = y
y + 2 = (3x2 + 10)(x − 1)

Answer 3

Yeah those don't look like quadratics to me :)

Answer 4

what.

Answer 5

what about B? That one is similar to D, right?

Answer 6

yes

Answer 7

so b and d are out?

Answer 8

I'd say so. They have a power greater than 2 when we distribute it out

Answer 9

can't be quadratic

Answer 10

quadratic equations will always have an exponent no larger than 2

Answer 11

In fact, I should say that quadratics will ALWAYS have an exponent of 2. :)

Answer 12

would it be this ?
y = 3x(5 − x) + 7

Answer 13

y= 15x - 3x^2+ 7

Answer 14

Yes, that's right. That is the form of a quadratic.

Answer 15

okay thanks ! :D

Answer 16

y = -3x^2 + 15x + 7 in standard form

Answer 17

The leading term will always have exponent 2

Answer 18

A is not quadratic because there is no squared variable.
D is not quadratic because on the right side, if you multiply the two binomials, you will have a term with x^3. This makes is a cubic equation, not a quadratic.
You were correct to eliminate A and D.

Now look at B and C carefully.