document.write( "Question 115037This question is from textbook
\n" ); document.write( ": Solve each system:\r
\n" ); document.write( "\n" ); document.write( "3p+2q=-2
\n" ); document.write( "9p-q=-6
\n" ); document.write( "

Algebra.Com's Answer #83873 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
\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( " \"3%2Ax%2B2%2Ay=-2\"
\n" ); document.write( " \"9%2Ax-1%2Ay=-6\"
\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( " \"2%2Ay=-2-3%2Ax\"Subtract \"3%2Ax\" from both sides
\n" ); document.write( "
\n" ); document.write( " \"y=%28-2-3%2Ax%29%2F2\" Divide both sides by 2.
\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=-1-%283%2F2%29%2Ax\" Now we've fully isolated y
\n" ); document.write( "
\n" ); document.write( " Since y equals \"-1-%283%2F2%29%2Ax\" we can substitute the expression \"-1-%283%2F2%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( " \"9%2Ax%2B-1%2Ahighlight%28%28-1-%283%2F2%29%2Ax%29%29=-6\" Replace y with \"-1-%283%2F2%29%2Ax\". Since this eliminates y, we can now solve for x.
\n" ); document.write( "
\n" ); document.write( " \"9%2Ax-1%2A%28-1%29-1%28-3%2F2%29x=-6\" Distribute -1 to \"-1-%283%2F2%29%2Ax\"
\n" ); document.write( "
\n" ); document.write( " \"9%2Ax%2B1%2B%283%2F2%29%2Ax=-6\" Multiply
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"9%2Ax%2B1%2B%283%2F2%29%2Ax=-6\" Reduce any fractions
\n" ); document.write( "
\n" ); document.write( " \"9%2Ax%2B%283%2F2%29%2Ax=-6-1\" Subtract \"1\" from both sides
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"9%2Ax%2B%283%2F2%29%2Ax=-7\" Combine the terms on the right side
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"%2818%2F2%29%2Ax%2B%283%2F2%29x=-7\" Make 9 into a fraction with a denominator of 2
\n" ); document.write( "
\n" ); document.write( " \"%2821%2F2%29%2Ax=-7\" Now combine the terms on the left side.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"cross%28%282%2F21%29%2821%2F2%29%29x=%28-7%2F1%29%282%2F21%29\" Multiply both sides by \"2%2F21\". This will cancel out \"21%2F2\" and isolate x
\n" ); document.write( "
\n" ); document.write( " So when we multiply \"-7%2F1\" and \"2%2F21\" (and simplify) we get
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"x=-2%2F3\" <---------------------------------One answer
\n" ); document.write( "
\n" ); document.write( " Now that we know that \"x=-2%2F3\", lets substitute that in for x to solve for y
\n" ); document.write( "
\n" ); document.write( " \"9%28-2%2F3%29-1%2Ay=-6\" Plug in \"x=-2%2F3\" into the 2nd equation
\n" ); document.write( "
\n" ); document.write( " \"-6-1%2Ay=-6\" Multiply
\n" ); document.write( "
\n" ); document.write( " \"-1%2Ay=-6%2B6\"Add \"6\" to both sides
\n" ); document.write( "
\n" ); document.write( " \"-1%2Ay=0\" Combine the terms on the right side
\n" ); document.write( "
\n" ); document.write( " \"cross%28%281%2F-1%29%28-1%29%29%2Ay=%280%2F1%29%281%2F-1%29\" Multiply both sides by \"1%2F-1\". This will cancel out -1 on the left side.
\n" ); document.write( "
\n" ); document.write( " \"y=0%2F-1\" Multiply the terms on the right side
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"y=0\" 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=0\"<---------------------------------Other answer
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So our solution is
\n" ); document.write( "
\n" ); document.write( " \"x=-2%2F3\" and \"y=0\"
\n" ); document.write( "
\n" ); document.write( " which can also look like
\n" ); document.write( "
\n" ); document.write( " (\"-2%2F3\",\"0\")
\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( " \"3%2Ax%2B2%2Ay=-2\"
\n" ); document.write( " \"9%2Ax-1%2Ay=-6\"
\n" ); document.write( "
\n" ); document.write( " we get
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " graph of \"3%2Ax%2B2%2Ay=-2\" (red) and \"9%2Ax-1%2Ay=-6\" (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 (\"-2%2F3\",\"0\"). 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 (\"-2%2F3\",\"0\") into the system of equations
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Let \"x=-2%2F3\" and \"y=0\". Now plug those values into the equation \"3%2Ax%2B2%2Ay=-2\"
\n" ); document.write( "
\n" ); document.write( " \"3%2A%28-2%2F3%29%2B2%2A%280%29=-2\" Plug in \"x=-2%2F3\" and \"y=0\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-6%2F3%2B0=-2\" Multiply
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-6%2F3=-2\" Add
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-2=-2\" Reduce. Since this equation is true the solution works.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So the solution (\"-2%2F3\",\"0\") satisfies \"3%2Ax%2B2%2Ay=-2\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Let \"x=-2%2F3\" and \"y=0\". Now plug those values into the equation \"9%2Ax-1%2Ay=-6\"
\n" ); document.write( "
\n" ); document.write( " \"9%2A%28-2%2F3%29-1%2A%280%29=-6\" Plug in \"x=-2%2F3\" and \"y=0\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-18%2F3%2B0=-6\" Multiply
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-18%2F3=-6\" Add
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-6=-6\" Reduce. Since this equation is true the solution works.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So the solution (\"-2%2F3\",\"0\") satisfies \"9%2Ax-1%2Ay=-6\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Since the solution (\"-2%2F3\",\"0\") satisfies the system of equations
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"3%2Ax%2B2%2Ay=-2\"
\n" ); document.write( " \"9%2Ax-1%2Ay=-6\"
\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" );