document.write( "Question 1010335: Please help me solve using substitution
\n" ); document.write( "2x - 5y = 11
\n" ); document.write( "-2x + 3y = -9
\n" ); document.write( "

Algebra.Com's Answer #625755 by MathLover1(20850)\"\" \"About 
You can put this solution on YOUR website!
\r
\n" ); document.write( "\n" ); document.write( "\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "\n" ); document.write( "
Solved by pluggable solver: Solving a linear system of equations by subsitution

\n" ); document.write( "
\n" ); document.write( " Lets start with the given system of linear equations
\n" ); document.write( "
\n" ); document.write( " \"2%2Ax-5%2Ay=11\"
\n" ); document.write( " \"-2%2Ax%2B3%2Ay=-9\"
\n" ); document.write( "
\n" ); document.write( " Now in order to solve this system by using substitution, we need to solve (or isolate) one variable. I'm going to choose y.
\n" ); document.write( "
\n" ); document.write( " Solve for y for the first equation
\n" ); document.write( "
\n" ); document.write( " \"-5%2Ay=11-2%2Ax\"Subtract \"2%2Ax\" from both sides
\n" ); document.write( "
\n" ); document.write( " \"y=%2811-2%2Ax%29%2F-5\" Divide both sides by -5.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Which breaks down and reduces to
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"y=-11%2F5%2B%282%2F5%29%2Ax\" Now we've fully isolated y
\n" ); document.write( "
\n" ); document.write( " Since y equals \"-11%2F5%2B%282%2F5%29%2Ax\" we can substitute the expression \"-11%2F5%2B%282%2F5%29%2Ax\" into y of the 2nd equation. This will eliminate y so we can solve for x.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-2%2Ax%2B3%2Ahighlight%28%28-11%2F5%2B%282%2F5%29%2Ax%29%29=-9\" Replace y with \"-11%2F5%2B%282%2F5%29%2Ax\". Since this eliminates y, we can now solve for x.
\n" ); document.write( "
\n" ); document.write( " \"-2%2Ax%2B3%2A%28-11%2F5%29%2B3%282%2F5%29x=-9\" Distribute 3 to \"-11%2F5%2B%282%2F5%29%2Ax\"
\n" ); document.write( "
\n" ); document.write( " \"-2%2Ax-33%2F5%2B%286%2F5%29%2Ax=-9\" Multiply
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-2%2Ax-33%2F5%2B%286%2F5%29%2Ax=-9\" Reduce any fractions
\n" ); document.write( "
\n" ); document.write( " \"-2%2Ax%2B%286%2F5%29%2Ax=-9%2B33%2F5\"Add \"33%2F5\" to both sides
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-2%2Ax%2B%286%2F5%29%2Ax=-45%2F5%2B33%2F5\" Make -9 into a fraction with a denominator of 5
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-2%2Ax%2B%286%2F5%29%2Ax=-12%2F5\" Combine the terms on the right side
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"%28-10%2F5%29%2Ax%2B%286%2F5%29x=-12%2F5\" Make -2 into a fraction with a denominator of 5
\n" ); document.write( "
\n" ); document.write( " \"%28-4%2F5%29%2Ax=-12%2F5\" Now combine the terms on the left side.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"cross%28%285%2F-4%29%28-4%2F5%29%29x=%28-12%2F5%29%285%2F-4%29\" Multiply both sides by \"5%2F-4\". This will cancel out \"-4%2F5\" and isolate x
\n" ); document.write( "
\n" ); document.write( " So when we multiply \"-12%2F5\" and \"5%2F-4\" (and simplify) we get
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"x=3\" <---------------------------------One answer
\n" ); document.write( "
\n" ); document.write( " Now that we know that \"x=3\", lets substitute that in for x to solve for y
\n" ); document.write( "
\n" ); document.write( " \"-2%283%29%2B3%2Ay=-9\" Plug in \"x=3\" into the 2nd equation
\n" ); document.write( "
\n" ); document.write( " \"-6%2B3%2Ay=-9\" Multiply
\n" ); document.write( "
\n" ); document.write( " \"3%2Ay=-9%2B6\"Add \"6\" to both sides
\n" ); document.write( "
\n" ); document.write( " \"3%2Ay=-3\" Combine the terms on the right side
\n" ); document.write( "
\n" ); document.write( " \"cross%28%281%2F3%29%283%29%29%2Ay=%28-3%2F1%29%281%2F3%29\" Multiply both sides by \"1%2F3\". This will cancel out 3 on the left side.
\n" ); document.write( "
\n" ); document.write( " \"y=-3%2F3\" Multiply the terms on the right side
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"y=-1\" Reduce
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So this is the other answer
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"y=-1\"<---------------------------------Other answer
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So our solution is
\n" ); document.write( "
\n" ); document.write( " \"x=3\" and \"y=-1\"
\n" ); document.write( "
\n" ); document.write( " which can also look like
\n" ); document.write( "
\n" ); document.write( " (\"3\",\"-1\")
\n" ); document.write( "
\n" ); document.write( " Notice if we graph the equations (if you need help with graphing, check out this solver)
\n" ); document.write( "
\n" ); document.write( " \"2%2Ax-5%2Ay=11\"
\n" ); document.write( " \"-2%2Ax%2B3%2Ay=-9\"
\n" ); document.write( "
\n" ); document.write( " we get
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " graph of \"2%2Ax-5%2Ay=11\" (red) and \"-2%2Ax%2B3%2Ay=-9\" (green) (hint: you may have to solve for y to graph these) intersecting at the blue circle.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " and we can see that the two equations intersect at (\"3\",\"-1\"). This verifies our answer.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " -----------------------------------------------------------------------------------------------
\n" ); document.write( " Check:
\n" ); document.write( "
\n" ); document.write( " Plug in (\"3\",\"-1\") into the system of equations
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Let \"x=3\" and \"y=-1\". Now plug those values into the equation \"2%2Ax-5%2Ay=11\"
\n" ); document.write( "
\n" ); document.write( " \"2%2A%283%29-5%2A%28-1%29=11\" Plug in \"x=3\" and \"y=-1\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"6%2B5=11\" Multiply
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"11=11\" Add
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"11=11\" Reduce. Since this equation is true the solution works.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So the solution (\"3\",\"-1\") satisfies \"2%2Ax-5%2Ay=11\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Let \"x=3\" and \"y=-1\". Now plug those values into the equation \"-2%2Ax%2B3%2Ay=-9\"
\n" ); document.write( "
\n" ); document.write( " \"-2%2A%283%29%2B3%2A%28-1%29=-9\" Plug in \"x=3\" and \"y=-1\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-6-3=-9\" Multiply
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-9=-9\" Add
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-9=-9\" Reduce. Since this equation is true the solution works.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So the solution (\"3\",\"-1\") satisfies \"-2%2Ax%2B3%2Ay=-9\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Since the solution (\"3\",\"-1\") satisfies the system of equations
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"2%2Ax-5%2Ay=11\"
\n" ); document.write( " \"-2%2Ax%2B3%2Ay=-9\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " this verifies our answer.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" );