Question

Prove that √2 - 3√5 is an irrational number​

Answer 1

Assume 2-3√5 be a rational no

therefore 2-3√5=a/b

hence √5=a-2b/3b

therefore a-2b/3b is a rational no

therefore √5 is a rational no

but we know that √5 is a irrational no

therefore our assumption was wrong that 2-3√5 is a rational no

therefore 2-3√5 is a irrational no