(4.4а+5.2b)²=(4.4a)²+(5.2b)²=19.36a²+27.04b²
(5.2x+3.6y)²=(5.2x)²+(3.6y)²=27.04x²+12.96y²
.......................................................
sin(pi-1)=sin1
2х+у=6
+∑3х-у=-2
5х=4
х=4:5
х=0.8
6√2+5√18= 6√2+5√(2*9) = 6√2+15√2=21√2