1.已知x,y满足2x+y=6,x-3y=1,求7y(x-3y)²-2(3y-x)³的值
问题描述:
1.已知x,y满足2x+y=6,x-3y=1,求7y(x-3y)²-2(3y-x)³的值
2.已知x+y=2,xy=-½,求x(x+y)²(1-y)-x(y+x)²的值
答
1因为x-3y=1所以7y(x-3y)^2-2(3y-x)^3=7Y+2因为x-3y=1所以x=3y+1所以7y+2=2x+y因为2x+y=6所以原式=62 x(x+y)²(1-y)-x(y+x)²=(x+y)^2(x-xy-x)=(x+y)^2*(-xy)=2^2*(1/2)=2...