Question: prove that 3 + 2 root 5 is in rational number?
Answer: PROOF: Let (3 + √5 ) be a rational number. ... So 3+2√5 = a/b where a,b are integers and are co primes and b is not equal to 0. => 2√5 = a/b - 3=> 2√5 = (a-3b)/b. => √5 = (a-3b)/2b.