Question

Using the quadratic function, provide the x intercepts of x^2+4x-21
Can someone just tell me what the quadratic function is..?

Answer 1

The quadratic function you have is x^2+4x-21
The graph will be a parabola

Answer 2

To find the x-intercepts, set your quadratic expression(function) equal to 0.
Then solve for x.

Answer 3

hmm
thats what i did @myininaya and i got x = -7 and 3 but the teacher wrote -2 and use quadratic function..

Answer 4

What is -2 suppose to be ?
Your x-intercepts are correct for this quadratic function.

Answer 5

Oh im just saying he took off 2 points and wrote use quadratic function.

Answer 6

Does he mean formula?

Answer 7

The quadratic formula is
\[x=\frac{-b \pm \sqrt{b^2-4ac}}{2a} \]

Answer 8

hmm ill try it.

Answer 9

Thanks for your help

Answer 10

Np. Good luck.

Answer 11

tnx

Answer 12

oh if you do the quadratic function you get 3 and -7. Can you check that for me? @myininaya

Answer 13

actually, never mind. I see his point but you could have just done (x+7) (x-3) and gotten the intercepts that way.

Answer 14

do you write it as (3,0) and (-7,0) though?

Answer 15

Yep
You could have factored or used the quadratic formula.

Answer 16

It is more proper to say the x-intercepts are (3,0) and (-7,0)
I would say it is informal to say they are 3 and -7

Answer 17

Yea, i understand.

Answer 18

Coolness.