If $l$ is the maximum value of $-3 x^2+4 x+1$ and $m$ is the minimum value of $3 x^2+4 x+1$, then the equation of the hyperbola having foci at $(l, 0),(7 \mathrm{~m}, 0)$ and eccentricity as 2 is

• Correct answer
  A

  $36 x^2-12 y^2=49$
• B

  $2 x^2-5 y^2=1$
• C

  $49 x^2-36 y^2=12$
• D

  $36 x^2-12 y^2=1$

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