Question

Which of the following is not an irrational number?
O 5+ √5
O (2+ √5)√5
O (2 + √5 )(2 - √5)
O 5√5​

Answer 1

Answer:

option 3 that is (2+√5)(2-√5)

this is because when we will apply the identity (a²-b²)=(a+b)(a-b)

then we will.get

(2)²-(√5)²

which is 4-5

that is -1

therefore -1 is an rational number.