Problem: If the graphs of 2y+x+3=0 and 3y+ax+2=0 are to meet at right angles, the value of a is:
Answer Choices:
A. ±32
B. −32
C. −23
D. 6
E. −6
Solution:
Let m1 be the slope of the line 2y+x+3=0, and m2, the slope of the line 3y+ax+2=0 For perpendicularity m1m2=−1
therefore (−21)(−3a)=−1 therefore a=−6