Question

If points (a,0),(0,b)and(1,1) are collinear, then $(a^{-1} + b^{-1})$ will be equal to :

• A. -1
• B. -2
• C. 1
• D. √2

Answer 1

Answer:

C. 1

1/2 [x₁(y₂-y₃) + x₂(y₃-y₁)+x₃(y₁-y₂)]=0

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

ab-a-b=0

ab=a+b

$1=\frac{a+b}{ab}$

$\frac{ 1}{a}+\frac{ 1}{b}=1$

$a^{-1}+b^{-1}=1$