help me understand how this is solved pls

T

thepcnerd

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Dec 4, 2006
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help me understand how this solve...

-3m+7n=2n+10 solve for n

book shows -3m+7n-2n=2n-2n+10
-3m+3m+5n=10+3m
5n=10+3m
_____
5

n=10+3m
______
5
but when i solve probelm

-3m+7n-7n=2n-7n+10 (i go from left to right not right to left like they are)
-3m=-5n+10
-3m-10=-5n+10-10
-3m-10=-5n
______
5

n=-3m-10
______
-5

What am i doing wrong,
 
thepcnerd said:
Code: 
help me understand how this solve...

-3m+7n=2n+10 solve for n

book shows -3m+7n-2n=2n-2n+10
                  -3m+3m+5n=10+3m
                   5n=10+3m
                      _____      -----------------------------
                        5        <-- divide >both< sides by 5 
                                 -----------------------------
n=10+3m
 ______
    5
but when i solve probelm

-3m+7n-7n=2n-7n+10 (i go from left to right not right to left like they are)
-3m=-5n+10
-3m-10=-5n+10-10
-3m-10=-5n
______     ----------------------------------------------
   5       <-- divide >both< sides by -5 (negative five) 
           ----------------------------------------------
n=-3m-10
  ______  --------------
    -5    <-- Brilliant 
          -------------- 
What am i doing wrong,

 -----------
 --> Nothing: n = (-3m - 10)/(-5) simplifies to (divide top and bottom by -1) to n = (3m + 10)/5, as per the given answer.|
 -----------
Click to expand...
 
you're not doing anything wrong. Both of those answers are correct. Just put in subsitutes for those variable and they both work out.
 
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