Question

(2-√5)² (2+√5)² find the value

Answer 1

Answer:

(2-√5)² (2+√5)

(2²+√5²-4√5)× (2²+√5²+4√5)

(4+5-4√5)×(4+5+4√5)

=(9-4√5)×(9+4√5)

= 9²- (4√5)² = 81 -80= 1

a²-b² = (a+b)(a-b)