If $(1, a),(b, 2)$ are conjugate points with respect to the circle $x^2+y^2=25$, then $4 a+2 b$ is equal to

• A

  $25$
• Correct answer
  B

  $50$
• C

  $100$
• D

  $150$

Solution

Since, $(1, a)$ and $(b, 2)$ are the conjugate point of a circle, therefore point $(1, a)$ satisfy the equation (iii), we get $$ \begin{aligned} b+2 a & =25 \\ \Rightarrow \quad 2 b+4 a & =50 \end{aligned} $$

Hence, the correct answer is option: 'B'.