## WynWynn 4 years ago Solve the system of equations by the addition method. Choose one answer. a. (-2, 1) b. (-2, -1) c. (2, 1) d. (2, -1)

1. WynWynn

2. gandalfwiz

THe addition method is adding one term to another to get a variable to cancel out.

3. gandalfwiz

You can multiply the equations by various numbers first to get the variables just right so they cancel

4. gandalfwiz

It doesn't matter what variable we choose to cancel out. Let's do x

5. WynWynn

ok!

6. gandalfwiz

We need the number in front of the first x to be the opposite of the second x, like 5, -5, or -3, 3, so they'll add to zero.

7. gandalfwiz

Lets multiply the first equation by 5 and the second one by -3 so we'll get a 15x and a -15x

8. gandalfwiz

5(-3x+7y=-1) -15x+35y=-5

9. gandalfwiz

second equation: -3(-5x-4y=14) 15x+12y=-42

10. gandalfwiz

Do you see what I did there?

11. gandalfwiz

wynwyn? uthere?

12. WynWynn

Yes yes yes i see!!

13. gandalfwiz

kk... now u just add the equations together. -15x+35y=-5 + 15x=12y=-42

14. gandalfwiz

(4 second equation: supposed to be 15x+12y=-42)

15. gandalfwiz

so. -15x+15x=0. 35y+12y=47y -5+-42=-47 0+47y=-47

16. gandalfwiz

Now just solve for y. 47y=-47 y=-1

17. gandalfwiz

Now that u know what y is, plug it back into an equation (it doesn't matter which) and solve for x

18. gandalfwiz

-3x+7y=-1 -3x+7(-1)=-1 -3x-7=-1 -3x=6 x=-2

19. WynWynn

ok

20. gandalfwiz

It looks like you want your final answer to be an ordered pair, like a point on a graph. a point is always in the form (x,y), so your final answer is -2,-1

21. gandalfwiz

choice b

22. WynWynn

Thank you so much!!!

23. gandalfwiz

welcome! Medal?

24. gandalfwiz

tnx :)

25. WynWynn

no problem! =D