document.write( "Question 126964: solve by substitution
\n" ); document.write( "1. 4x + 5y= 6
\n" ); document.write( " y=2x - 10\r
\n" ); document.write( "\n" ); document.write( "2. 4x-3y=0
\n" ); document.write( " y=x+1
\n" ); document.write( "

Algebra.Com's Answer #92985 by MathLover1(20849)\"\" \"About 
You can put this solution on YOUR website!

\n" ); document.write( "1. \r
\n" ); document.write( "\n" ); document.write( "\"4x+%2B+5y=+6\"
\n" ); document.write( " \"y=2x+-10\".....write in standard form\r
\n" ); document.write( "\n" ); document.write( "\"4x+%2B+5y=+6\"
\n" ); document.write( " \"-2x+%2B+y=+-10\"\r
\n" ); document.write( "
\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( " \"4%2Ax%2B5%2Ay=6\"
\n" ); document.write( " \"-2%2Ax%2B1%2Ay=-10\"
\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=6-4%2Ax\"Subtract \"4%2Ax\" from both sides
\n" ); document.write( "
\n" ); document.write( " \"y=%286-4%2Ax%29%2F5\" 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=6%2F5-%284%2F5%29%2Ax\" Now we've fully isolated y
\n" ); document.write( "
\n" ); document.write( " Since y equals \"6%2F5-%284%2F5%29%2Ax\" we can substitute the expression \"6%2F5-%284%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%2B1%2Ahighlight%28%286%2F5-%284%2F5%29%2Ax%29%29=-10\" Replace y with \"6%2F5-%284%2F5%29%2Ax\". Since this eliminates y, we can now solve for x.
\n" ); document.write( "
\n" ); document.write( " \"-2%2Ax%2B1%2A%286%2F5%29%2B1%28-4%2F5%29x=-10\" Distribute 1 to \"6%2F5-%284%2F5%29%2Ax\"
\n" ); document.write( "
\n" ); document.write( " \"-2%2Ax%2B6%2F5-%284%2F5%29%2Ax=-10\" Multiply
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-2%2Ax%2B6%2F5-%284%2F5%29%2Ax=-10\" Reduce any fractions
\n" ); document.write( "
\n" ); document.write( " \"-2%2Ax-%284%2F5%29%2Ax=-10-6%2F5\" Subtract \"6%2F5\" from both sides
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-2%2Ax-%284%2F5%29%2Ax=-50%2F5-6%2F5\" Make -10 into a fraction with a denominator of 5
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-2%2Ax-%284%2F5%29%2Ax=-56%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-%284%2F5%29x=-56%2F5\" Make -2 into a fraction with a denominator of 5
\n" ); document.write( "
\n" ); document.write( " \"%28-14%2F5%29%2Ax=-56%2F5\" Now combine the terms on the left side.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"cross%28%285%2F-14%29%28-14%2F5%29%29x=%28-56%2F5%29%285%2F-14%29\" Multiply both sides by \"5%2F-14\". This will cancel out \"-14%2F5\" and isolate x
\n" ); document.write( "
\n" ); document.write( " So when we multiply \"-56%2F5\" and \"5%2F-14\" (and simplify) we get
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"x=4\" <---------------------------------One answer
\n" ); document.write( "
\n" ); document.write( " Now that we know that \"x=4\", lets substitute that in for x to solve for y
\n" ); document.write( "
\n" ); document.write( " \"-2%284%29%2B1%2Ay=-10\" Plug in \"x=4\" into the 2nd equation
\n" ); document.write( "
\n" ); document.write( " \"-8%2B1%2Ay=-10\" Multiply
\n" ); document.write( "
\n" ); document.write( " \"1%2Ay=-10%2B8\"Add \"8\" to both sides
\n" ); document.write( "
\n" ); document.write( " \"1%2Ay=-2\" Combine the terms on the right side
\n" ); document.write( "
\n" ); document.write( " \"cross%28%281%2F1%29%281%29%29%2Ay=%28-2%2F1%29%281%2F1%29\" Multiply both sides by \"1%2F1\". This will cancel out 1 on the left side.
\n" ); document.write( "
\n" ); document.write( " \"y=-2%2F1\" Multiply the terms on the right side
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"y=-2\" 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=-2\"<---------------------------------Other answer
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So our solution is
\n" ); document.write( "
\n" ); document.write( " \"x=4\" and \"y=-2\"
\n" ); document.write( "
\n" ); document.write( " which can also look like
\n" ); document.write( "
\n" ); document.write( " (\"4\",\"-2\")
\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( " \"4%2Ax%2B5%2Ay=6\"
\n" ); document.write( " \"-2%2Ax%2B1%2Ay=-10\"
\n" ); document.write( "
\n" ); document.write( " we get
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " graph of \"4%2Ax%2B5%2Ay=6\" (red) and \"-2%2Ax%2B1%2Ay=-10\" (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 (\"4\",\"-2\"). 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 (\"4\",\"-2\") into the system of equations
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Let \"x=4\" and \"y=-2\". Now plug those values into the equation \"4%2Ax%2B5%2Ay=6\"
\n" ); document.write( "
\n" ); document.write( " \"4%2A%284%29%2B5%2A%28-2%29=6\" Plug in \"x=4\" and \"y=-2\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"16-10=6\" Multiply
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"6=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 (\"4\",\"-2\") satisfies \"4%2Ax%2B5%2Ay=6\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Let \"x=4\" and \"y=-2\". Now plug those values into the equation \"-2%2Ax%2B1%2Ay=-10\"
\n" ); document.write( "
\n" ); document.write( " \"-2%2A%284%29%2B1%2A%28-2%29=-10\" Plug in \"x=4\" and \"y=-2\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-8-2=-10\" Multiply
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-10=-10\" Add
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-10=-10\" Reduce. Since this equation is true the solution works.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So the solution (\"4\",\"-2\") satisfies \"-2%2Ax%2B1%2Ay=-10\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Since the solution (\"4\",\"-2\") satisfies the system of equations
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"4%2Ax%2B5%2Ay=6\"
\n" ); document.write( " \"-2%2Ax%2B1%2Ay=-10\"
\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" ); document.write( "2.\r
\n" ); document.write( "\n" ); document.write( "\"4x+-+3y=+0\"
\n" ); document.write( " \"y=x+%2B1\".....write in standard form\r
\n" ); document.write( "\n" ); document.write( "\"4x+-+3y=+0\"
\n" ); document.write( " \"-x+%2B+y=+1\"\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( " \"4%2Ax-3%2Ay=0\"
\n" ); document.write( " \"-1%2Ax%2B1%2Ay=1\"
\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( " \"-3%2Ay=0-4%2Ax\"Subtract \"4%2Ax\" from both sides
\n" ); document.write( "
\n" ); document.write( " \"y=%280-4%2Ax%29%2F-3\" Divide both sides by -3.
\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=0%2B%284%2F3%29%2Ax\" Now we've fully isolated y
\n" ); document.write( "
\n" ); document.write( " Since y equals \"0%2B%284%2F3%29%2Ax\" we can substitute the expression \"0%2B%284%2F3%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( " \"-1%2Ax%2B1%2Ahighlight%28%280%2B%284%2F3%29%2Ax%29%29=1\" Replace y with \"0%2B%284%2F3%29%2Ax\". Since this eliminates y, we can now solve for x.
\n" ); document.write( "
\n" ); document.write( " \"-1%2Ax%2B1%2A%280%29%2B1%284%2F3%29x=1\" Distribute 1 to \"0%2B%284%2F3%29%2Ax\"
\n" ); document.write( "
\n" ); document.write( " \"-1%2Ax%2B0%2B%284%2F3%29%2Ax=1\" Multiply
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-1%2Ax%2B0%2B%284%2F3%29%2Ax=1\" Reduce any fractions
\n" ); document.write( "
\n" ); document.write( " \"-1%2Ax%2B%284%2F3%29%2Ax=1%2B0\"Add \"0\" to both sides
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-1%2Ax%2B%284%2F3%29%2Ax=1\" Combine the terms on the right side
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"%28-3%2F3%29%2Ax%2B%284%2F3%29x=1\" Make -1 into a fraction with a denominator of 3
\n" ); document.write( "
\n" ); document.write( " \"%281%2F3%29%2Ax=1\" Now combine the terms on the left side.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"cross%28%283%2F1%29%281%2F3%29%29x=%281%2F1%29%283%2F1%29\" Multiply both sides by \"3%2F1\". This will cancel out \"1%2F3\" and isolate x
\n" ); document.write( "
\n" ); document.write( " So when we multiply \"1%2F1\" and \"3%2F1\" (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( " \"-1%283%29%2B1%2Ay=1\" Plug in \"x=3\" into the 2nd equation
\n" ); document.write( "
\n" ); document.write( " \"-3%2B1%2Ay=1\" Multiply
\n" ); document.write( "
\n" ); document.write( " \"1%2Ay=1%2B3\"Add \"3\" to both sides
\n" ); document.write( "
\n" ); document.write( " \"1%2Ay=4\" Combine the terms on the right side
\n" ); document.write( "
\n" ); document.write( " \"cross%28%281%2F1%29%281%29%29%2Ay=%284%2F1%29%281%2F1%29\" Multiply both sides by \"1%2F1\". This will cancel out 1 on the left side.
\n" ); document.write( "
\n" ); document.write( " \"y=4%2F1\" Multiply the terms on the right side
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"y=4\" 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=4\"<---------------------------------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=4\"
\n" ); document.write( "
\n" ); document.write( " which can also look like
\n" ); document.write( "
\n" ); document.write( " (\"3\",\"4\")
\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( " \"4%2Ax-3%2Ay=0\"
\n" ); document.write( " \"-1%2Ax%2B1%2Ay=1\"
\n" ); document.write( "
\n" ); document.write( " we get
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " graph of \"4%2Ax-3%2Ay=0\" (red) and \"-1%2Ax%2B1%2Ay=1\" (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\",\"4\"). 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\",\"4\") into the system of equations
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Let \"x=3\" and \"y=4\". Now plug those values into the equation \"4%2Ax-3%2Ay=0\"
\n" ); document.write( "
\n" ); document.write( " \"4%2A%283%29-3%2A%284%29=0\" Plug in \"x=3\" and \"y=4\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"12-12=0\" Multiply
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"0=0\" Add
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"0=0\" Reduce. Since this equation is true the solution works.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So the solution (\"3\",\"4\") satisfies \"4%2Ax-3%2Ay=0\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Let \"x=3\" and \"y=4\". Now plug those values into the equation \"-1%2Ax%2B1%2Ay=1\"
\n" ); document.write( "
\n" ); document.write( " \"-1%2A%283%29%2B1%2A%284%29=1\" Plug in \"x=3\" and \"y=4\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"-3%2B4=1\" Multiply
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"1=1\" Add
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"1=1\" Reduce. Since this equation is true the solution works.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So the solution (\"3\",\"4\") satisfies \"-1%2Ax%2B1%2Ay=1\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Since the solution (\"3\",\"4\") satisfies the system of equations
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"4%2Ax-3%2Ay=0\"
\n" ); document.write( " \"-1%2Ax%2B1%2Ay=1\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " this verifies our answer.
\n" ); document.write( "
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