(√3+√7) x (√3-√7) : (2√5-4√2)

(√3 + √7)(√3 - √7) : (2√5 - 4√2)
= ((√3)² - (√7)²)(2√5 + 4√2) / (2√5 - 4√2)(2√5 + 4√2)
= (3 - 7)(2√5 + 4√2) / ((2√5)² - (4√2)²)
= (-4)(2√5 + 4√2) / (20 - 32)
= -4/(-8) (2√5 + 4√2)
= 1/2 (2√5 + 4√2)
= √5 + 2√2