Question

What is the equation of the line that passes through (3,-1) and (4,7)

Answer 1

gradient = 7-(-1)/4-3
= 8
when x = 3, y = -1,
y = 8x + c
-1 = 8(3) + c
c = -1 - 24
= -25
the equation of the line is y = 8x - 25.

Answer 2

Using y=mx+b the answer would be y=8(x-3)-1.