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Home Q & A Board Science-Related Homework Help Mathematics
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rjframe rjframe
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12 years ago
How would I do this?

Solve each system of equations by using substitution.

1) m+n=20
m-n= -4

Solve each system of equations by using elimination.

1) 2p-q=5
3p+q=5
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Replies
wrote...
#1
12 years ago
1) m+n=20 Rightwards Arrow n=20-m
m-n= -4
m-(20-m) = -4 Leftwards Arrow 2--m substituted for n
m-20+m =-4
2m = 16
m = 8
8+n=20
n = 12

2p-q=5
3p+q=5
Add the two equations getting:
5p = 10
p = 2
2(2) -q = 5
-q = 1
q=-1
wrote...
#2
12 years ago
1) m=20-n
now sub m into the second line equation so

20-2n=-4
-2n=-24
n=12

2)
2p-q=5
3p+q=5
are simultaneous equations first make the p's equal so:
6p-3q=15
6p+2q=10

Then take them away to eliminate the 6p.
-5q=5
q=-1

Then put into any one of original eq to solve.
2p-(-1)=5
2p=4
p=2
Answer accepted by topic starter
rjblayzrjblayz
wrote...
#3
Posts: 48
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12 years ago
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