COORDINATES A2

If m(4,6), B(7,10) and C(a,2) are collinear, find a.

 

Solution

 

x1=4, y=6, x2=7, y2=10, x3=a, y3=2.

 

y2 – y1  =   y3 – y2

x2 – x1     x3 – x2

 

10 – 6  =   2 – 10        

7 – 4        a – 7

 

 

4    =   -8         Now we cross multiply

3       a - 7

 

 

 

4(a-7) = 3 x -8

4a – 28 = -24

4a   = -24 + 28

4a  = 4

a= ⁴/₄ =1

 

Hence a = 1.

 

TRY THIS………………..

 

If m(2,-3), B(4,5) and C(w,29) are collinear, find w.