What form would you use to write the equation of a line if you knew the slope and x-intercept? explain.

You know the slope and the point (x1,0) where x1 is the x  coordinate of the x intercept.

You use the point slope form of the line:-

y - y1  = m(x - x1)  where m = slope and (x1,y1) is a point on the line.

here y1 = 0  so the  equation would be

y = m(x - x1)