Problem: A straight line passing through the point (0,4) is perpendicular to the line x−3y−7=0. Its equation is:
Answer Choices:
A. y+3x−4=0
B. y+3x+4=0
C. y−3x−4=0
D. 3y+x−12=0
E. 3y−x−12=0
Solution:
Method I. y=m2x+b,4=m2⋅0+b∴b=4. Also m2m1=31m2=−1∴m2=−3
∴y=−3x+4 or y+3x−4=0
Method II. x−0y−4=−3∴y−4=−3x or y+3x−4=0.