Question

Determine the intercepts of the line that passes through the following points. (-10,-28) , (-6,-21) , ( -2,-14)

Answer 1

The line through (a,b) and (c,d) is

(c-a)(y-b) = (d-b)(x-a)

Picking the last two points,

(-2 - -6)(y - -21) = (-14 - -21)(x - -6)

4(y+21) = 7(x+6)

When x=0

4y + 84 = 42

4y = -42

y = -21/2

Answer: -21/2

We never used the first point, let's check it's on the line


4(y+21) = 7(x+2)


4(-28 + 21) = -28

7(-10 + 6) = -28, good