For line 1: Let (x1,y1)=(4,5) and (x2,y2)=(0,−2).
Slope=y2−y1x2−x1=−2−50−4
Slope =−7−4=74=m1
For line 2:(x1,y2)=(2,−3),(x2,y2)=(−5,1)
Slope=y2−y1x2−x1=1−(−3)−5−2=1+3−7
Slope=47=−47=m2
m1×m2=74×−47=−1
The product of their slopes is −1
∴ The two lines are perpendicular.