Question 176308: A> 2x-3y+5y=2
B> 3x+2y-z=12
C> x+4y+z=18
FIRST STEP IN THE ELIMINATION OF THE VARIABLE Y
A) MULTIPLY EQUATION B BY -2 AAND ADD EQUATIONS B AND C
B) MULTIPLY B BY -2 AND ADD EQUAIONS A AND B
C) OTHER, IF SO... HOW?
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! A> 2x-3y+5y=2
B> 3x+2y-z=12
C> x+4y+z=18
FIRST STEP IN THE ELIMINATION OF THE VARIABLE Y
A) MULTIPLY EQUATION B BY -2 AAND ADD EQUATIONS B AND C
B) MULTIPLY B BY -2 AND ADD EQUAIONS A AND B
C) OTHER, IF SO... HOW?
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I'll assume you meant 5z in eqn A.
You need to eliminate a variable, y is ok, from 2 eqns using, leaving 2 eqns with 2 unknowns.
Step A is good, gives an eqn in x and z.
Step B is not good, it eliminates x, not y.
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A better choice is to eliminate x, because its coeff in eqn C is 1, making it easy to scale to match eqns A and B.
Whatever variable you choose to eliminate, you have to eliminate in from 2 eqns.
Try eliminating x. Email me if you need more help. (the thank you notes go to my email.)
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An update: z is even better for elimination, as B and C have one z in them. Just add B and C and z is gone.
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