If the line passing through the points (2, a) and (5, - 3) is parallel to the line passing through the points (4, 8) and (- 5, a + 1) , what is the value of a?

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Parallel lines have the same gradient

Gradient of the first line=dy/dx=a-(-3)/2-5

gradient of the second line =8-(a+1)/4-(-5)

a+3/-3 =7-a/9

Cross multiplication

9 (a+3) =-3 (7-a)

9 a + 27 = -21 +3 a

6a=-48

a = -8

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