Question

find the value of a if the lines ax+3y=5 and 2x+(a+1)y=6 are perpendicular

Answer 1

2a+3(a+1)=0
solve for a
2a+3a+3=0
5a=-3
a=-3/5

Answer 2

a1*a2+b1*b2=0 is the condition for perpendicularity

so, a*2+3*(a+1)=0 where a1=a;a2=2;b1=3;b2=(a+1)
2a+3a+3=0
5a+3=0
a=-3/5