## anonymous one year ago Write the quadratic function in vertex form. y = x2 + 8x + 18

1. anonymous

i know you have to Subtract 18 from both sides: y - 18 = x^2 + 8x Complete the square by adding 16 to both sides: y - 18 + 16 = x^2 + 8x + 16 y - 2 = x^2 + 8x + 16 Express x^2 + 8x + 16 in binomial square form: y - 2 = (x + 4)^2 Add 2 to both sides: y = (x + 4)^2 + 2

2. anonymous

You can use the vertex formula to figure out the max height: t=−b2a t=−6402(−16) t=20 Next you'll need to insert t = 20 into the given equation: h(20) = - 16(20)^2 + 640(20)

3. anonymous

then simplify the expression on the right to solve for h(20)

4. anonymous

how would you solve for h(20)

5. anonymous

h(20) = - 16(20)^2 + 640(20)

6. anonymous

@saseal

7. anonymous

how did it turn from t into h?

8. anonymous

i have no idea im using this

9. anonymous
10. anonymous

11. anonymous

ok the general form of a parabola looks like this $x^2=4py$ and the standard forms are the messy quadratic equations

12. anonymous

13. anonymous

like that graph right?

14. anonymous

$x^2+8x+18=0$since you cant factorize this you need to complete the square$x^2+8x=-18$$x^2+8x+(\frac{ 8 }{ 2 })^2=-18+(\frac{ 8 }{ 2 })^2$$x^2+8x+16=-18+16$$(x+4)^2=-2$

15. anonymous

dont worry about that graph thing yet

16. anonymous

ok

17. anonymous

thank you

18. anonymous

@nono266

19. anonymous

you can understand it so far?

20. anonymous

kinda

21. anonymous

22. anonymous

lol

23. anonymous

that means you dont understand...

24. anonymous

would it be - instead of the +

25. anonymous

$(x+4)^2=-2$$(x+4)^2+2=0$

26. anonymous

ugh yes!