Question

The answer of $\sqrt{42+ \sqrt{42+ \sqrt{42+....∞} } }$ is

Answer 1

 S=(42+(42+(42+..)^0.5)^0.5)^0.5
    => S=(42+S)^0.5
            squaring both sides:
           S^2=42+S
           S^2-S-42=0
           solving the quadratic you will get  S=7,-6.

Answer 2

 => S=(42+S)^0.5
            squaring both sides:
           S^2=42+S
           S^2-S-42=0
using quadratic equation= x is -6 or 7