## anonymous 4 years ago these are really hard for me.. Can someone help? The vertex of y = 9 - 8x - x2 is (-4, 25) True or False What is the vertex for the function? y = x2 - 4x - 3 Anwsers: (-1, 2) (0, -3) (1, -6) (2, -7)

1. anonymous

I am assuming that when you say x2 you mean $x^2$

2. anonymous

yes

3. anonymous

(2,-7)

4. anonymous

Can you help me with the previous ones i posted?

5. anonymous

To do this, we find the axis of symmetry, which (in standard form of ax^2 + bx + c) is x = -b/a which in this case is -8, then we plug that into x to get the y-value of the vertex, 9, so the vertex is (-8, 9)

6. anonymous

so false

7. anonymous

can you help me with these two? What are the values of a, b, and c in the function? List them in order with commas, such as 1,-2,3. y = -2x2 + 5x - 4 What is the vertex for the function? (You will want to find the axis of symmetry first.) Write as an ordered pair, leaving no spaces, such as (1,-4). y = -3x2 + 6x

8. anonymous

look at the standard form i posted above.

9. anonymous

i dnt get it

10. anonymous

$y = ax^2 + bx + c$

11. anonymous

??

12. anonymous

now you can do the first one, then look how I found the axis of symmetry above, -b/a, in this case on the second question -6/-3 = 2

13. anonymous

Ok, What about the first one?

14. anonymous

$y = ax^2 + bx + c$ this is the standard form of a quadratic equation, quadratic means that the highest exponent is 2 such as $x^2$

15. anonymous

OK,

16. anonymous

find the coefficients of x^2 and x in their respective places relative to a and b, c is the constant number on the end (-4)

17. anonymous

i got it :)

18. anonymous

One more? Thanks so much for your help! Which coefficient in the function tells us that the parabola for the function will point downward? y = -2x2 + 5x - 4

19. anonymous

Anwsers: -2 5 -4

20. anonymous

the direction of the parabola depends on whether the coefficient of the x^2 term is positive or negative. If it is positive such as 5x^2 it will point up, but -3x^2 would point down. In this case -2 is the coefficient which means it points downward

21. anonymous

ohhh kk!!

22. anonymous

HOW DO I FIGURE THIS OUT $6\sqrt{2} - 3\sqrt{2}$