Posted by im stuck on this one!! on Tuesday, January 18, 2011 at 10:55pm.
Substitution means we express one variable in terms of another, and substitute this expression into the second equation.
m+2n=1 ...(1)
5m+3n=-23 ...(2)
From (1), we have
m+2n=1
subtract 2n from each side to get
m+2n-2n=1-2n
m=1-2n ...(1a)
Substitute m from (1a) into (2) to get:
5m+3n=-23
5(1-2n)+3n=-23
5-10n+3n =-23
-7n = -23 -5
-7n = -28
n=(-28)/(-7)=4 ...(2a)
Substitute n from (2a) into (1a)
m=1-2n
=1-2*4
=-7
So m=-7, n=4
Last step!!
Substitute the values of m and n into equations (1) and (2) to verify that the solutions are correct:
m+2n=1 ...(1)
-7+2*4=-7+8=1 OK
5m+3n=-23 ...(2)
5*(-7)+3*4
=-35+12
=-23 OK
THANKS!!!!!!! great explaining!!!
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