SOLUTION: solve using elimination method: 3r-4s=1, 9r-12s= -3 I am not sure how the elimination method works. I keep referring back to the substitution method and getting it all wrong.

Click here to see ALL problems on Expressions-with-variables

Question 732040: solve using elimination method: 3r-4s=1, 9r-12s= -3
I am not sure how the elimination method works. I keep referring back to the substitution method and getting it all wrong.
Found 2 solutions by Vladdroid, Edwin McCravy:
Answer by Vladdroid(91) (Show Source):
You can put this solution on YOUR website!
click on the math equation to get the steps and the answer. CHEERS
click here.........click here

Answer by Edwin McCravy(20059) (Show Source):
You can put this solution on YOUR website!

This is an inconsistent system and has no solutions. 3r - 4s = 1 9r - 12s = -3 Let's try doing it first by substitution. Solve the first equation for r 3r - 4s = 1 3r = 1 + 4s r = Substitute in 9r - 12s = -3 9 - 12s = -3 3(1+4s) - 12s = -3 3 + 12s - 12s = -3 3 + 0s = -3 0s = -6 There is no value of s such that when multiplied by 0 will give -6. Thus this system has no solution. ---------------------- Now let's try doing it by elimination: 3r - 4s = 1 9r - 12s = -3 Multiply the first equation through by -3 -9s + 12s = -3 9s - 12s = -3 Add the two equations term by term: -9s + 12s = -3 9s - 12s = -3 -------------- 0s + 0s = -6 No matter what values we substitute for r and s, the left side will be 0 and the right side -6. So there can be no solutions. The system is inconsistent. Here are the graphs of the two equations: They run parallel and therefore do not intersect and do not have any common solution. Edwin