Question

find the values of a and b if the points are A(-2,1),B(a,b) and C(4,-1) are collinear and a-b=1

Answer 1

points (-2,1),(a,b) and (4,-1) are collinear
Using the point-slope formula, 
(-2,1 and
(4,-1) m = 2/ -6 = -1/3
(-2,1),
(a,b)  |Question states: (a-b) = 1, a = 1+b
(1-b) / (-2-(1+b)) |substituting for a
(1-b)/ (-3 - b) = -1/3
-1(-3-b) = 3(1-b) |cross multiplying
3 + b = 3 - 3b
4b = 0
b = 0 and a = 1 (a = 1+b)
CHECKING our Answer***
(-2,1),
(1,0) m = 1/-3

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