okay i really don't understand this problem.

Question

It says:

Prove the point-slope equation property which is :

Point-slope equation(an nonvertical line with slope m and containing a point (X1,Y1) has the point-slope equation of y-y1=m(x-x1).

Now show that any point (x2,y2) on the line described must satisfy the equation, and that any point satisfying the equation must be on the line described.