Question

$(2 + \sqrt{5) (2 - \sqrt{5)} }$
simplify​

Answer 1

Answer:

using the identity

(a+b)(a-b) = a²-b²

here (a+b) = (2+√5)

(a-b) = (2-√5)

(2+√5)(2-√5)

2²- (√5)²

4 - 5

= -1