先化简,再求值.已知x=-2,y=125分之一,求x(3x-2y)+(2x+y)²+(2x-y)(x+y)-3(xy+10)的值
问题描述:
先化简,再求值.已知x=-2,y=125分之一,求x(3x-2y)+(2x+y)²+(2x-y)(x+y)-3(xy+10)的值
答
原式=3x(2)-2xy+4x(2)+y(2)+4xy+2x(2)+2xy-xy-y(2)-3xy-30
=9x(2)-30
=36-30
=6
答
x(3x-2y)+(2x+y)²+(2x-y)(x+y)-3(xy+10)
=3x^2-2xy+4x^2+4xy+y^2+2x^2+xy-y^2-3xy-30
=9x^2-30
x=-2,
=36-30
=6