Question 161198
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{{{9x-9y=27}}} --------------> eqn 1
{{{7y-3x=-11}}} ------------> eqn 2
Multiply eqn 2 by {{{highlight(3)}}}:
{{{7y-3x=-11}}}-------> {{{21y-9x=-33}}} -----> eqn 3
Add eqn 1 & eqn 3:
{{{12y=-6}}} ----> {{{system(9x-9y=27,21y-9x=-33)}}}, eliminates {{{9x}}}
Continuing,
{{{cross(12)y/cross(12)=-6/12=-1/2}}} divide 12 to isolate y
{{{y=-1/2}}}
via eqn 1:
{{{9x-9(-1/2)=27}}}
{{{9x+9/2=27}}}
{{{9x=27-9/2=(54-9)/2}}} get LCD of left term
{{{18x=45}}}, cross multiply
{{{cross(18)x/cross(18)=cross(45)2.5/cross(18)}}}
{{{x=2.5}}}
(2.5,-0.5) ANSWER
Check via eqn 2:
{{{7*-1.5-3*2.5=-11}}}
{{{-3.5-7.5=-11}}}
{{{-11=-11}}}
Thank you,
Jojo</pre>