2) (79-65)(79+65)/420 = 14*144/420 = 2016/420 = 4,8
3) (92-48)(92+48)/(27-17)(27+17) = 44*140/10*44 = сократим 44 с 44 и 140 с 10, получим = 14
4) (63-27)(63+27)/(83-79)(83+79) = 36*90/4*162= сократим 36 и 4, получим = 9*90/162 = сократим 9 и 62 = 90/18 = 5