elimination of variable by cross multiplication of linear equation, 3x+4y=22,-4x+5y=43

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1 Answer

3x+4y=22

-4x+5y=43

Cross-multiply by multiplying first eqn by 4 and the second by 3:

12x+16y=88

-12x+15y=129

Now add: 31y=217 so y=217/31=7 and 3x+4*7=22 by substitution.

3x=22-28=-6 so x=-2.

Answer: x=-2, y=7

 

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