How to build the equation of the line

The point-slope formula lets you build the equation of the line, you just need the slope and one point:

Y-Y1=m(X-X1)

f you have a line with slope 3 that passes through point (1,2) then we can build the equation of the line by substituting the point and the slope into the formula.

Y-2=3(X-1)
Y-2= 3X -3
Y= 3X -3 + 2
Y= 3x -1

The final answer is Y= 3x-1