## overtonka 2 years ago Solve each system of equations by substitution -3v-3x=15 5v+x=-29

1. tkhunny

Divide the first by 3 and something magic may pop out.

2. skullpatrol

I tried to teach you this yesterday and you refused to learn?

3. overtonka

I did not refuse I just didn't get it

4. tkhunny

Well, @overtonka, I think @skullpatrol would be delighted to see you make a better effort, today. Divide the first equation by 3 and show what you get.

5. overtonka

-1v-1x=5

6. tkhunny

Super! Any suggestion what we should do next? Hint: I didn't have you divide by 3 just for fun.

7. overtonka

solve for one of the variables?

8. skullpatrol

Yes!

9. overtonka

so 1v=5-1x?

10. skullpatrol

Now what (hint: use the name of the method)

11. tkhunny

Since we are using substitition, that would be the things to do. Please abandon those silly-looking '1's. We don't usually write those unless we are trying to make a point.

12. overtonka

ok so v-x=5?

13. tkhunny

No, why did you UNsolve? Please "solve for one of the variables".

14. overtonka

v=5-x?

15. skullpatrol

Correct.

16. overtonka

so plug that in to the other equation?

17. skullpatrol

Substitution principle: An expression maybe replaced by another expression that has the same value If \$\$a=b\$\$then b maybe substituted for a in any expression.

18. skullpatrol

|dw:1362010398136:dw|

19. tkhunny

It's your big chance. Let's see the substitution!