document.write( "Question 557977: don't know why the substitution method my head wont engage in. I am a college student , this on is driving me crazy x+y=4,y=3x using substitution method. in need of serious help. \n" ); document.write( "

Algebra.Com's Answer #362849 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
A simple example of substitution is:
\n" ); document.write( "(1) $\"+x+%2B+y+=+5+\"$
\n" ); document.write( "(2) $\"+y+=+3+%2B+x+\"$
\n" ); document.write( "Substitute (2) into (1)
\n" ); document.write( "You can do this because $\"+y+\"$ appears
\n" ); document.write( "in both equations
\n" ); document.write( "(1) with the substitution is:
\n" ); document.write( "(1) $\"+x+%2B+%28+3+%2B+x+%29+=+5+\"$
\n" ); document.write( "(1) $\"+2x+%2B+3+=+5+\"$
\n" ); document.write( "(1) $\"+2x+=+2+\"$
\n" ); document.write( "(1) $\"+x+=+1+\"$
\n" ); document.write( "and, since
\n" ); document.write( "(2) $\"+y+=+3+%2B+x+\"$
\n" ); document.write( "(2) $\"+y+=+3+%2B+1+\"$
\n" ); document.write( "(2) $\"+y+=+4+\"$
\n" ); document.write( "-----------------
\n" ); document.write( "Here's your problem:
\n" ); document.write( "(1) $\"+x+%2B+y+=+4+\"$
\n" ); document.write( "(2) $\"+y+=+3x+\"$
\n" ); document.write( "I will substitute (2) into (1)
\n" ); document.write( "(1) $\"+x+%2B+%28+3x+%29+=+4+\"$
\n" ); document.write( "(1) $\"+4x+=+4+\"$
\n" ); document.write( "(1) $\"+x+=+1+\"$
\n" ); document.write( "and, since
\n" ); document.write( "(2) $\"+y+=+3x+\"$
\n" ); document.write( "(2) $\"+y+=+3%2A1+\"$
\n" ); document.write( "(2) $\"+y+=+3+\"$
\n" ); document.write( "So, the solution is the point (1,3)
\n" ); document.write( "Here's a plot of the lines
\n" ); document.write( "(1) $\"+x+%2B+y+=+4+\"$
\n" ); document.write( "(2) $\"+y+=+3x+\"$
\n" ); document.write( " $\"+graph%28+400%2C+400%2C+-6%2C+6%2C+-6%2C+6%2C+-x+%2B+4%2C+3x+%29+\"$
\n" ); document.write( " \n" ); document.write( "

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