Quantitative Aptitude Ques 992

Question: $ \sqrt{12+\sqrt{12+\sqrt{12+…}}} $ is equal to

Options:

A) 3

B) 4

C) 6

D) 2

Show Answer

Answer:

Correct Answer: A

Solution:

  • Let $ x=\sqrt{12+\sqrt{12+\sqrt{12+…}}} $ On squaring both sides, we get $ x^{2}=12+\sqrt{12+\sqrt{12+…}} $

$ \Rightarrow $ $ x^{2}-12=x $

$ \Rightarrow $ $ x^{2}-x-12=0 $

$ \Rightarrow $ $ x^{2}-4x+3x-12=0 $

$ \Rightarrow $ $ x,(x-4)+3,(x-4)=0 $

$ \Rightarrow $ $ (x+3)(x-4)=0 $

$ \Rightarrow $ $ x=4, $ $ -3 $ Since, x will be positive number.

$ \therefore $ $ x=4, $ $ x\ne 3 $