How do you solve the following system: 8x - y = 13 , 5x-9y=-23 8x−y=13,5x−9y=−23?

1 Answer
Roy Ø.
Jun 19, 2018

x=140/67=2 6/67x=14067=2667
y=249/67 =3 48/67y=24967=34867

Explanation:

System of equations:
1) 8x-y=13 => y=8x-138x−y=13⇒y=8x−13
2) 5x-9y=-23 => 9y=5x+235x−9y=−23⇒9y=5x+23
1) inserted in 2) gives:
3) 9(8x-13)=5x+23 => 72x-117=5x+239(8x−13)=5x+23⇒72x−117=5x+23
67x=140 => x=140/67=2 6/6767x=140⇒x=14067=2667
Inserted in 1):
y=8*2 6/67-13=16 48/67 - 13=3 48/67y=8⋅2667−13=164867−13=34867

Check: 5x-9y=5*2 6/67 - 9*3 48/67=-235x−9y=5⋅2667−9⋅34867=−23

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