document.write( "Question 324900: Line 1 crosses the y-axis at y=5 and passes through the point (2,1). Line 2 is perpendicular to Line 1 and crosses the x axis at x=-3. What is the equation for line 2? \n" ); document.write( "
Algebra.Com's Answer #232666 by nerdybill(7384)\"\" \"About 
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Line 1 crosses the y-axis at y=5 and passes through the point (2,1). Line 2 is perpendicular to Line 1 and crosses the x axis at x=-3. What is the equation for line 2?
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\n" ); document.write( "First, determine slope of line 1:
\n" ); document.write( "From: \"crosses the y-axis at y=5\" we get one point (0,5)
\n" ); document.write( "And, using the other given point (2,1) we can calculate the slope:
\n" ); document.write( "(y2-y1)/(x2-x1) = (5-1)/(2-0) = 4/2 = 2
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\n" ); document.write( "Since line 2 is perpendicular (the slopes are negative reciprocals):
\n" ); document.write( "Let m = slope of line 2
\n" ); document.write( "then
\n" ); document.write( "2m = -1
\n" ); document.write( "m = -1/2 (Line 2 slope)
\n" ); document.write( "That, along with \"crosses the x axis at x=-3\" gives us a point at (-3, 0)
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\n" ); document.write( "Plug the above into the \"point-slope\" formula:
\n" ); document.write( "y - y1 = m(x - x1)
\n" ); document.write( "y - 0 = (-1/2)(x - (-3))
\n" ); document.write( "y = (-1/2)(x + 3)
\n" ); document.write( "y = (-1/2)x - 3/2 (this is what they're looking for)
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