2x-y=3 ==>4x-2y=6 (1)
4x+3y=1 (2)
(2)-(1)
5y=-5
y=-1
2x=3+y=3-1=2
x=1
∴5y（2x-y）²-2（y-2x)^3
=5*(-1)*3^2-2*(-1-2)^3
=-45-2*(-3)^3
=-45+2*27
=-45+54
=9