## EmmaH 2 years ago PLEASE HELP!!!! Solve the system, using substitution. One point for correct steps, one point for correct ordered pair, (a,b). a + b = 4 and 2a + 3b = 11 i tried to solve for a but ended up with 1/-5 i dont think thats right....

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2. seidi.yamauti

a+b=4 2a+3b=11 a=4-b 2(4-b)+3b=11 (substituing a as found) a=4-b 8+b=11 a=4-b b=3 so, a=1 and b=3

3. EmmaH

a=4-b 2(4-b)+3b=11 i get that but how did ypu go from that to a=4-b 8+b=11

4. seidi.yamauti

you need first to isolate a or b in one of the equations, and use this on the other. I have skipped one or two steps, but if you do correctly, the answer (a,b)=(1,3) will be found

5. seidi.yamauti

2(4-b) = 8-2b, write it and keep solving

6. seidi.yamauti

This problem is about solving what is called 'linear system'. You have some equations with letters and need to find what are their values. Further you will see that not all of this kind of systems can be solved (when there are more letters than equations) - but you can just ignore it by now tell me when you're done, it just a matter of practice to solve it better an faster

7. EmmaH

ok question: in 2(4-b)+3b=11 would it equal 8-b+3b=11 or 8-2b+3b=11?

8. seidi.yamauti

8-2b+3b=11

9. seidi.yamauti

because the 2 multipies both 4 and -b in 2(4-b)

10. EmmaH

this is what i got 8-b+3b=11 8+2b=11 2b=11-8 2b=3 2b/2=3/2

11. seidi.yamauti

re-do it haha it is 8-2b+3b=11 but what you've done is right if it was 8-b+3b=11

12. taylorstenger

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13. seidi.yamauti

kind of what taylor said... You need to do all by yourself, and just ask for some tips. Because it is when you think alone that you really understand. try and try and try. It's hard, but sometime there will be just the right answer

14. taylorstenger

Yup. U cant just go on the internet and find answers for everything and anything. Theres a reason its in ur text books, and theres a reason teachers teach it to u. If u paid attention, u wouldnt be askin questions on OpenStudy ;-)

15. EmmaH

im not trying to gte an easy answer i honestly dont understand this also i didnt respond bcs my inter net went out

16. seidi.yamauti

I was just complementing. Just to say, first step, you can ask a lot about your doubt, but with time, you will do it without any help. haha

17. EmmaH

im really confused about what to do after i get -2b=3 can you please continue to help me?

18. seidi.yamauti

i'm here. Let's see..

19. seidi.yamauti

where is -2b=3 ?

20. EmmaH

8-2b=11 -2b=11-8 -2b=3

21. seidi.yamauti

you have a+b=4 2a+3b=11 then, you use ANY of these equations to isolate a letter in the case, I've used the first and came up with a=4-b (so, from now on, that's what a is) you could also do it in the second, but that's too much work

22. seidi.yamauti

I isolated a, but it could be also b. both correct

23. EmmaH

thisd is what ive done a + b = 4 and 2a + 3b = 11 2(4-b)+3b=11 8-b+3b=11 8-2b=11 -2b=11-8 -2b=3

24. EmmaH

what next?

25. seidi.yamauti

2(4-b)+3b=11 8-b+3b=11 This is not right, because when you multiply a number times something in parenthesis, everything inside is multiplied so 2(4-b)+3b=11 what comes next?

26. EmmaH

8-2b+3b=11?

27. seidi.yamauti

yes!

28. seidi.yamauti

and i guess, if you go back to my first post, it will make more sense now

29. EmmaH

8-1b=11 -1b=11-8 -1b=3 -1b/-1=3/-1 b=-3 is that right

30. seidi.yamauti

nonononoooo you've got 8-2b+3b=11 which is equal to 8+b=11 not 8-b=11

31. EmmaH

8+b=11 b=3 ??

32. seidi.yamauti

YES! hahahaha

33. EmmaH

XD

34. EmmaH

(1,3) ?

35. seidi.yamauti

That's it :)

36. EmmaH

thank you for taking the time to help me!

37. seidi.yamauti