document.write( "Question 693720: David has been working for his company since 1990. Each year he gets a $2100 raise, in 1998 he earned one and a half times as much as he earned in 1990.
\n" ); document.write( "Write an equation in the form of y=mx+b that models David's salary y in terms of number of years x since he started working there. What was his salary in 1998? How much will he earn in 2005? \n" ); document.write( "

Algebra.Com's Answer #427515 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
I can call 1990, the year he started work, $\"+x+=+0+\"$
\n" ); document.write( "1991 will be $\"+x+=+1+\"$
\n" ); document.write( "The slope will be ( change in y ) / ( change in x ), so
\n" ); document.write( " $\"+m+=+2100+%2F+1+\"$ ( the 1 stands for 1 year )
\n" ); document.write( " $\"+m+=+2100+\"$
\n" ); document.write( "given:
\n" ); document.write( " $\"+y%288%29+=+1.5%2Ay%280%29+\"$
\n" ); document.write( "-----------------
\n" ); document.write( "So far I have
\n" ); document.write( " $\"+y+=+2100x+%2B+b+\"$
\n" ); document.write( "Now I can say
\n" ); document.write( " $\"+y%280%29+=+2100%2A0+%2B+b+\"$
\n" ); document.write( " $\"+y%280%29+=+b+\"$
\n" ); document.write( "and also
\n" ); document.write( " $\"+y%288%29+=+2100%2A8+%2B+b+\"$
\n" ); document.write( " $\"+1.5%2Ay%280%29+=+2100%2A8+%2B+b+\"$
\n" ); document.write( " $\"+1.5%2Ab+=+16800+%2B+b+\"$
\n" ); document.write( " $\"+1.5b+-+b+=+16800+\"$
\n" ); document.write( " $\"+.5b+=+16800+\"$
\n" ); document.write( " $\"+b+=+16800+%2F+.5+\"$
\n" ); document.write( " $\"+b+=+33600+\"$
\n" ); document.write( "--------------
\n" ); document.write( "Now I have the final equation
\n" ); document.write( " $\"+y+=+2100x+%2B+33600+\"$
\n" ); document.write( "---------------------
\n" ); document.write( "His salary in 1998 was
\n" ); document.write( " $\"+y+=+2100%2A8+%2B+33600+\"$
\n" ); document.write( " $\"+y+=+16800+%2B+33600+\"$
\n" ); document.write( " $\"+y+=+50400+\"$
\n" ); document.write( "$50,400
\n" ); document.write( "-----------
\n" ); document.write( "In 2005 he will earn
\n" ); document.write( " $\"+y+=+2100%2A15+%2B+33600+\"$
\n" ); document.write( " $\"+y+=+31500+%2B+33600+\"$
\n" ); document.write( " $\"+y+=+65100+\"$
\n" ); document.write( "$65,100
\n" ); document.write( "-----------
\n" ); document.write( "Check:
\n" ); document.write( "Is the slope between $\"+x+=+0+\"$ and $\"+x+=+15+\"$
\n" ); document.write( "equal to $\"+2100+\"$ ?
\n" ); document.write( " $\"+%28+65100+-+33600+%29+%2F+%28+15+-+0+%29+\"$
\n" ); document.write( " $\"+31500+%2F+15+=+2100+\"$
\n" ); document.write( "OK
\n" ); document.write( "---------
\n" ); document.write( "Here's a plot:
\n" ); document.write( " $\"+graph%28+400%2C+400%2C+-2%2C+16%2C+-10000%2C+100000%2C+2100x+%2B+33600+%29+\"$ \r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

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