## anonymous 5 years ago I am doing quadratic functions Can someone help me solve this y=-2x^2+11x-12

1. anonymous

Solve it for y = 0? Are you familiar with the quadratic formula?

2. anonymous

yes but this is +or - a=-2,b=11 c=-12

3. anonymous

I know how to do the formula but have done 10 problems but don't come up with the correct answer

4. anonymous

Those are the correct values for a, b, and c.

5. anonymous

$11+-\sqrt{(11^2-4(-2)(-12)}$

6. anonymous

I have done the numbers in parenthesis first what do you come up with

7. anonymous

$$11^2 - 4(-2)(-12) = 25$$

8. anonymous

okay that is what I got

9. anonymous

x=4

10. anonymous

So you should have $$\frac{-11 \pm \sqrt{25}}{2(-2)}$$

11. anonymous

I have to have a + and - answer

12. anonymous

They could both be + or - depending on your other values.

13. anonymous

But you will have 2 unless the part under the sqrt is 0

14. anonymous

I have $11+-\sqrt{25?}\div-4$

15. anonymous

It should be -11, not 11. Recall that the quadratic formula is $ax^2 + bx +c=0 \implies x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}$

16. anonymous

i got x=-9 and -14 over-4

17. anonymous

okay that is right I have it in front of me

18. anonymous

x = (-11 + 5 )/(-4) = -6/-4 = 3/2 x = (-11 - 5)/(-4) = -16/-4 = 4

19. anonymous

if you let y be 0 than after you can write your equation as -2x^2+11x-12=0 or you can write this as 2x^2-11x+12=0 from this equation you can get the correct answer

20. anonymous

You won't have any negative values for the x intercepts of this graph.

21. anonymous

True I have been working on this too long I think thank you

22. anonymous

Certainly =)