Slope DS

Recall that slope = (y2 - y1)/(x2-x1). So the slope is (u - (-s))/(t-r) = (u+s)/(t-r).

(1) r > t. Subtract r from both sides and get 0 > t - r . This tells us that the denominator is negative. Numerator could be positive or negative so cannot determine the sign of the slope. INSUFFICIENT.

(2). u > -s. Add s to both sides and get u + s > 0. This tells us that the numerator is positive. The denominator could be positive or negative so we cannot determine the sign of the slope. INSUFFICIENT.

(1)+(2). (1) tells us that the denominator is negative and (2) tells us that the numerator is positive. So the slope is negative.

The answer is C.

ok one question here.....

now since the negative co-ordinate is given a negative sign...then why cant the other co-ordinates tht are without sighs considered positive.



bcos if we consider them as positive then A is sufficient to answer.

I think you're assuming that because s has a negative sign s is negative.

The question only says that the line L passes through points (r,-s) and (t,u)

statement 1 says that r > t
for example r = 3, t = 2, u = 2 and s = -3 gives a slope 1
while r = 3, t= 2, u = 2 and s = 3 gives a slope -5

so statement 1 is insufficient