-4(-0.8х+2у)-(4.2х-у)=3.2х-8у-4.2х+у=-х-7у
при х=2 у=-1 -х-7у=-2-7*-1=5
44:8=5(ост.4) 8*5+4=44
73:8=9(ост.1) 8*9+1=73
85:9=9(ост.4) 9*9+1=85
1/51 и 1/68 = 1/(3*17) и 1/(4*17) = 4/204 и 3/208
5/36 и 7/54 = 5/(2*2*9) и 7/(2*3*9) = 15/108 и 14/108
9/35 и 11/42 = 9/(7*5) и 11/(7*6) = 54/210 и 55/210
4/49 и 5/63 = 4/(7*7) и 5/(7*9) = 36/441 и 35/441
15/98 и 13/72 = 15/(2*49) и 13/(2*36) = 540/3528 и 637/3528
Корень из 225 - 14 = 15 - 14 = 1