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complex questions on slopes

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complex questions on slopes

by coolgirl26 » Sun Apr 19, 2009 12:31 pm
a straight line passes thorugh points a,b and c,d ..is slope of line less than 0



Okay so
1) a-c * b-d <0

2) product of intercepts of line on x axis and on y axis greater than o



so waht are these saying..can you give me good explanation and
short cuts to solve

answer:D
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Source: — Data Sufficiency |
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by mayuran23 » Sun Apr 19, 2009 12:45 pm
Okay, so we're given 2 points on the line, (a,b) and (c,d).

According to the slope formula, slope = (y2 - y1) / (x2 - x1)

in this case, slope = (d - b) / (c - a)

for a slope to be negative, either (d-b) or (c-a) must be negative (not both)

Stmt 1: (a-c) * (d-b) < 0, so either (a-c) or (d-b) are negative, thereby making the slope negative according to the formula above

sufficient

Stmt 2: the product of the x and y intercepts are greater than 0

for this to occur, either both the x and y intercepts must be positive, or both the x and y intercepts must be negative

if the line is sloping down (from top left to bottom right), then both intercepts will be negative OR both intercepts will be positive

if the line is sloping up, then one will be positive and the other will be negative

and a downward sloping line always has a negative slope

sufficient

hope this helps
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by ketkoag » Wed Apr 22, 2009 1:23 am
i think there is a | | sign for the slope i.e. slope is |y2-y1|/|x2-x1|. so statement 1 is insufficient according to me.

experts please help..
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by rossmj » Wed Apr 22, 2009 8:43 am
definitely no abs in slope formula, otherwise how would we ever get a negative slope.
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