document.write( "Question 155243: Find the equation of the line that represents the number of book sales\r
\n" ); document.write( "\n" ); document.write( "1,11,500 and 4,13,600 \n" ); document.write( "

Algebra.Com's Answer #114345 by nerdybill(7384) $\"\"$ $\"About$

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The problem gives you two points on the line:
\n" ); document.write( "(1,11500) and (4,13600)
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\n" ); document.write( "This site describes linear equations quite well:
\n" ); document.write( "http://en.wikipedia.org/wiki/Linear_equation
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\n" ); document.write( "The strategy is to put in a \"two-point\" form:
\n" ); document.write( "Given two points:
\n" ); document.write( "(h,k) and (p,q), and has slope m = (q−k)/(p−h)
\n" ); document.write( "y-k = m(x-h)
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\n" ); document.write( "So, if:
\n" ); document.write( "(h,k) and (p,q) were:
\n" ); document.write( "(1,11500) and (4,13600)
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\n" ); document.write( "Then, to find the slope:
\n" ); document.write( "m = (q−k)/(p−h)
\n" ); document.write( "m = (13600−11500)/(4−1)
\n" ); document.write( "m = (13600−11500)/(4−1)
\n" ); document.write( "m = 2100/3
\n" ); document.write( "m = 700
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\n" ); document.write( "Now, we plug it all into:
\n" ); document.write( "y-k = m(x-h)
\n" ); document.write( "y-11500 = 700(x-1)
\n" ); document.write( "y-11500 = 700x-700
\n" ); document.write( "y = 700x+10800 (this is what they're looking for)
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