Equations of Straight Lines

Do Now

ABC is a triangle with vertices A(1,1), B(4,7) and C(8,a).

(a) Find the gradient of the line AB.

(7-1)/(4-1) = 6/3 = 2

The gradient of BC is -½

(b) Find the value of a.

(a-7)/(8-4) = -1/2

(a-7)/(4) = -1/2

2(a-7)=-4

2a - 14 = -4

2a = 10

A =5

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