Question

what is the equation of the line which includes points (1, 5) and (-2, -7)?

Answer 1

Given two points, the equation of the line can be known by,
                          y - y1 = ((y2 - y1)/(x2 - x1)) (x - x1)
Substituting the known values,
                          y - 5 = ((-7 - 5) / (-2 - 1)) (x - 1) 
The final equation of the line is,
                              y = 4x + 1