document.write( "Question 162864: Solve by substitution or elimination:
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document.write( "2x-3y+z=14
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document.write( "4x+2y-5z=-3
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document.write( "x+y+2z=1 \n" );
document.write( "
Algebra.Com's Answer #120071 by elima(1433)![]() ![]() ![]() You can put this solution on YOUR website! I'll use elimination to solve; \n" ); document.write( "2x-3y+z=14 \n" ); document.write( "4x+2y-5z=-3 \n" ); document.write( "x+y+2z=1 \n" ); document.write( "================== \n" ); document.write( "First add two equations together to eliminate a variable; \n" ); document.write( "4x+2y-5z=-3 - multiply equation by 2 so you can eliminate the z; \n" ); document.write( "x+y+2z=1 - multiply equation by 5 so you can eliminate the z; \n" ); document.write( "========================= \n" ); document.write( "2(4x+2y-5s=-3) \n" ); document.write( "8x+4y-10z=-6 \n" ); document.write( "5(x+y+2z=1) \n" ); document.write( "5x+5y+10z=5 \n" ); document.write( "=============== \n" ); document.write( "8x+4y-10z=-6 \n" ); document.write( "5x+5y+10z=5 \n" ); document.write( "----------- \n" ); document.write( "13x+9y=-1 \n" ); document.write( "==================== \n" ); document.write( "Now choose two others to eliminate the z; \n" ); document.write( "2x-3y+z=14 - multiply by -2 \n" ); document.write( "x+y+2z=1 \n" ); document.write( "======================= \n" ); document.write( "-2(2x-3y+z=14) \n" ); document.write( "-4x+6y-2z=-28 \n" ); document.write( "x+y+2z=1 \n" ); document.write( "------------ \n" ); document.write( "-3x+7y=-27 \n" ); document.write( "==================== \n" ); document.write( "Now add the two new equations together to eliminate another variable; \n" ); document.write( "13x+9y=-1 - multiply by -7 \n" ); document.write( "-3x+y=-27 - multiply by 9 \n" ); document.write( "============================ \n" ); document.write( "-7(13x+9y=-1) \n" ); document.write( "-91x-63y=-14 \n" ); document.write( "9(-3x+7y=-27) \n" ); document.write( "-21x+63y=-243 \n" ); document.write( "============================= \n" ); document.write( "-91x-63y=7 \n" ); document.write( "-27x+63y=-243 \n" ); document.write( "------------- \n" ); document.write( "-118x=-236 \n" ); document.write( "x=2 \n" ); document.write( "======================= \n" ); document.write( "Now that we have the x, let's plug it into one of the new equations and solve for y; \n" ); document.write( "13(2)+9y=-1 \n" ); document.write( "26+9y=-1 \n" ); document.write( "9y=-27 \n" ); document.write( "y=-3 \n" ); document.write( "=========================== \n" ); document.write( "We have our x and y, let's plug them in and get the z; \n" ); document.write( "x+y+2z=1 \n" ); document.write( "2+-3+2z=1 \n" ); document.write( "-1+2z=1 \n" ); document.write( "2z=2 \n" ); document.write( "z=1 \n" ); document.write( "========================= \n" ); document.write( "check; \n" ); document.write( "2x-3y+z=14 \n" ); document.write( "2(2)-3(-3)+1=14 \n" ); document.write( "4+9+1=14 \n" ); document.write( "14=14 \n" ); document.write( "check; \n" ); document.write( "4x+2y-5z=-3 \n" ); document.write( "4(2)+2(-3)-5(1)=-3 \n" ); document.write( "8-6-5=-3 \n" ); document.write( "-3=-3 \n" ); document.write( ":) \n" ); document.write( " \n" ); document.write( " |