Find equation of the line which is perpendicular to the line y=5x + 9
and has y-intercept = 6.
Two lines y1 = k1*x+a1 (here k1=5 and a1=9) and y2 = k2*x+a2 are perpendicular if k1*k2 = -1. So, required line has the slope k2 = -1/5. To feet the condition about y-intercept we'll set a2 = 6. So, required line is given by equation y2 = -x/5+6.