Question

If the lines ax+y+1=0, x+by+1=0 and x+y+c=0 (a,b,c being distinct and different from 1) are concurrent, then

(a) 0

(b) 1

(c) \(\frac{1}{a+b+c}\)

(d) None

Answer 1

c₂ →c₂ –c₁ ,c₃ →c₃ –c₁

a(b-1)(c-1)-(1-a)(c-1)+(1-a)(1-b)=0

divide by (1-a)(1-b)(1-c) we get