Question 214870
Solve by elimination method

{{{9x-9y=9}}}  Equation A
{{{7y-3x=-5}}}  Equation B


Step 1.  Multiply Equation by 3 and add to equation A


{{{9x-9y=9}}} Equation A
{{{-9x+21y=-15}}}  Equation B-1 after multiplying by 3

Adding above equations yield,

{{{-9y+21y=9+(-15)}}}

{{{12y=-6}}}

{{{y=-6/12=-1/2}}}

Step 2.  Substitute y=-1/2 into one of the equations say Equation A


{{{9x-9y=9}}}  Equation A


{{{9x-9(-1/2)=9}}}


{{{x+1/2=1}}}


{{{x=1/2}}}


Step 3.   Solution is (1/2,-1/2) or {{{x=1/2}}} and {{{y=-1/2}}}


As a check, let's solve by elimination


*[invoke linear_substitution "x", "y", 9,-9, 9, -3, 7, -5]


Same result as before...


I hope the above steps were helpful.


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Good luck in your studies!


Respectfully,
Dr J