A line passes through (2a, 7) and (8,5a). If its slope is 4,
find a.

__Solution__
x1=2a, y1 = 7, x2 = 8, y2 = 5a

Slope(m)
=

__y2 – y1__
x2 – x1

4 =

__5a – 7__
8 – 2a

__4__=

__5a – 7__[cross multiplying]

1 8 – 2a

4(8
– 2a) = 5a – 7

32
– 8a = 5a – 7

32
– 8a + 7 = 5a

32
+ 7 = 5a+ 8a

39
= 13a

__39__=

__13a__

13 13

3
= a

__Hence a = 3__

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