A (3,-5), B(-2, a), C(18, 1) are collinear. a=?
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Step-by-step explanation:
x1=3 x2=-2 x3=18
y1=-5 y2=a y3=1
collinear= 1/2[x1(y2-y3)+x2(y3-y1)+x3(y1-y2)]
=1/2[3(a-1) +(-2)(1-(-5))+18(-5-a)]
=1/2[(3a-3)+(-2)(1+5)+(-90-18a)]
=1/2[3a-3-12-90-18a]
=1/2[-15a-105]
=-15a/2-105/2
15a/2=-105/2
15a=-105
a=-105/15
a=-7
hope it's help to you. So pls make me as brainliest
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