document.write( "Question 13251: What is the difference between a line whose slope is undefined, and a line with a slope of zero? \n" ); document.write( "
Algebra.Com's Answer #6682 by longjonsilver(2297)\"\" \"About 
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x=3, x=-16 etc have an undefined gradient...they are vertical lines. In essence their gradients are infinite.\r
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\n" ); document.write( "\n" ); document.write( "However, y=3 or y=-16 etc have a zero gradient...they are horizontal lines.\r
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