## EmmaH Group Title cansomeone show me how to solve this? Use the quadratic formula to find the zeros of the function. y = 16x2 + 40x + 25 {-1.25, 1.25} {-1.25} {-4, 5} {-0.8 one year ago one year ago

1. amistre64 Group Title

do you recall the setup of the quadratic formula?

2. EmmaH Group Title

$\frac{ -b \pm \sqrt{b ^{2}-4ac} }{ 2a }$

3. amistre64 Group Title

good, and the general form of a quadratic is: $ax^2 + bx + c$ pull the numbers from the problem that relate to the abc parts and what do you get worked out?

4. EmmaH Group Title

a=16 b=40 and 25=c

5. amistre64 Group Title

good, i notice that there are no - signs to worry about so that looks good so far

6. EmmaH Group Title

what do i do next?

7. amistre64 Group Title

plug in those numbers into their abc parts in the formula, the rest is just math for maths sake

8. amistre64 Group Title

$x=\frac{ -b \pm \sqrt{b ^{2}-4ac} }{ 2a }$ $x=\frac{ -40 \pm \sqrt{40^{2}-4(16)(25)} }{ 2(16) }$

9. EmmaH Group Title

$\frac{ -40\pm \sqrt{40^{2}-4(16)(25)} }{ 2(16) }$ is that right?

10. amistre64 Group Title

looks good to me :)

11. EmmaH Group Title

ok then i get 40 pm 16-96/32?

12. EmmaH Group Title

but i would end up eith a negative number....

13. amistre64 Group Title

$\frac{ -40\pm \sqrt{40^{2}-4(16)(25)} }{ 2(16) }$ $\frac{ -40\pm \sqrt{4^2(10)^2-4(4^2)(25)} }{ 2(16) }$ $\frac{ -40\pm 4\sqrt{10^2-4(25)} }{ 2(16) }$ $\frac{ -40\pm 4\sqrt{25(4)-4(25)} }{ 2(16) }$ $\frac{ -40}{ 2(16) }$ $\frac{ -40}{ 2(4.4) }$ $\frac{ -10}{ 2(4) }$ $\frac{ -5}{ 4 }$

14. EmmaH Group Title

you lost me at the second one you did how did you get all the the ^2?

15. amistre64 Group Title

40^2 = (4*10)^2 = 4*10 * 4*10 = 4^2 * 10^2 but you dont have to do exactly what i did

16. EmmaH Group Title

uuuuh.....im sorry you lost me all i know is im suppose to square 40 is that what you were doin?

17. EmmaH Group Title

@amistre64 ?

18. amistre64 Group Title

i was doing some manipulations so that i didnt have to worry about computing large numbers and such; i simplified it down to where i recognized the sqrt part goes to zero.

19. amistre64 Group Title

but 40^2 - 4(16)(25) = 0

20. EmmaH Group Title

ui havent learned taht i think im suppose to just use the big numbers

21. amistre64 Group Title

then math it out for maths sake, youll get big numbers that finally reduce and simplify

22. EmmaH Group Title

i tried but i keep getting teh wrong number when i have 40^2-4(16)(5) i get 0 right? i get 1,600 -1,600 and i cant square thaty

23. amistre64 Group Title

what does 1600 - 1600 equal?

24. EmmaH Group Title

0 -_- i cant square 0

25. amistre64 Group Title

sure you can, 0*0 = 0

26. EmmaH Group Title

oooooh......

27. EmmaH Group Title

so -40 pm 0/32?

28. amistre64 Group Title

$\frac{ -40\pm \sqrt{40^{2}-4(16)(25)} }{ 2(16) }$ $\frac{ -40\pm \sqrt{1600-1600} }{ 2(16) }$ $\frac{ -40\pm \sqrt{0} }{ 2(16) }$ $\frac{ -40\pm 0 }{ 2(16) }$ $\frac{ -40}{ 2(16) }$

29. amistre64 Group Title

yes /32 is fine as well

30. EmmaH Group Title

THANK YOU SO MUCH!!!!!

31. amistre64 Group Title

youre welcome

32. EmmaH Group Title

so its -40/32?

33. amistre64 Group Title

yes, which a calculator should be able to put into decimals for you

34. EmmaH Group Title

-1.25?

35. amistre64 Group Title

correct

36. EmmaH Group Title

thank you!