document.write( "Question 27823: Use substitution to solve the linear system.\r
\n" ); document.write( "\n" ); document.write( "x + 4y = 21
\n" ); document.write( "4x + 2y = 6\r
\n" ); document.write( "\n" ); document.write( "AND Different problem:\r
\n" ); document.write( "\n" ); document.write( "Find the solution to the system by graphing.\r
\n" ); document.write( "\n" ); document.write( "x + y = 6
\n" ); document.write( "4x - y = 7 \n" ); document.write( "

Algebra.Com's Answer #15165 by bmauger(101) $\"\"$ $\"About$

You can put this solution on YOUR website!
$\"x%2B4y=21\"$ Subtract 4y from both sides:
\n" ); document.write( " $\"x=21-4y\"$ Now use 21-4y to substitute for x in the second equation:
\n" ); document.write( " $\"4x%2B2y=6\"$
\n" ); document.write( " $\"4%2821-4y%29%2B2y=6\"$ Distribute:
\n" ); document.write( " $\"84-16y%2B2y=6\"$ Rearrange:
\n" ); document.write( " $\"-14y=-78\"$ Divide:
\n" ); document.write( " $\"y=14%2F78\"$
\n" ); document.write( " $\"y=7%2F39\"$
\n" ); document.write( " $\"x=21-4%287%2F39%29\"$
\n" ); document.write( " $\"x=791%2F39%29\"$ \r
\n" ); document.write( "\n" ); document.write( "Problem 2:
\n" ); document.write( " $\"graph+%28300%2C+300%2C+-3%2C+8%2C+-3%2C+8%2C%0D%0A6-x%2C%0D%0A4x-7%29\"$
\n" ); document.write( "Graphically it looks like: (2.5, 3.5) or x=2.5 & y=3.5\r
\n" ); document.write( "\n" ); document.write( "Checking $\"2.5%2B3.5=6\"$ Check.
\n" ); document.write( " $\"4%282.5%29-3.5=6.5\"$ Pretty close... close as you should expect to get finding the answer through graphing. \n" ); document.write( "

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