## Saiyan one year ago Need help I will give medal

1. Saiyan

2. campbell_st

well the y- intercept is given (0, -4.5) so that means you choices are the 1st or 3rd equations... so substitute -2 into both equations and see which gives y = -23.5 then when you have 1 equation just check against the 3rd point

3. Saiyan

ok hold on

4. Saiyan

I put 2 in for x and still didnt get -23.5

5. campbell_st

which equation did you use..?

6. Saiyan

1 and 3

7. Saiyan

get out of here

8. Saiyan

hello

9. campbell_st

well in equation 1 $-2.5 \times (-2)^2 + 4.5 \times (-2) - 4.5 = ?$

10. Saiyan

sorry -10+-9-4.5

11. campbell_st

so is that equal to the y value you need..?

12. Saiyan

-24.5

13. Saiyan

its not -23.5 if that is what you are asking

14. campbell_st

you may want to check that -19 - 4.5 = -23.5 u

15. Saiyan

oops missed that

16. Saiyan

so its the first one

17. campbell_st

well you may like the check with the 3rd point... just to make sure

18. Saiyan

ok i will hold on

19. Saiyan

for the second one i got -4.5

20. campbell_st

I think you need to check your calculations $-2.5\times (4)^2 + 4.5 \times 4 - 4.5 = ?$

21. Saiyan

i put in a -2

22. campbell_st

I'm using the 3rd point on the 1st equation...

23. Saiyan

but its -26.5

24. campbell_st

Isn't that what you want, for the 3rd point in the 1st equation...

25. Saiyan

i just want to know how to do this

26. campbell_st

the 3rd point x = 4 -2.5 * 4^2 = -40 4.5 * 4 = 18 - 4.5 ---------- -26.5 so the 1st equation is true for the 3 points... I wouldn't go any further

27. campbell_st

ok... so do you understand that the y- intercept for the points given is (0, -4.5)..?

28. Saiyan

ohhhh ok i get what your saying

29. campbell_st

so substitute x = 0 into the equations and the only ones that give y = -4.5 are the 1st and 3rd so next use the point x = -2 y = -23.5 substitute x = -2 and see if you get y = -23.5 this happens in the 1st equation, the 3rd equation gives y = -17.5 I think... so lastly use the 3rd point to check the 1st equation is the answer... the point (4, -26.5) substitute x = 4 and see if you get -26.5 that's a simple process that uses elimination...using some observation and arithmetic

30. Saiyan

ok thx