化简求值:

题目

化简求值:
(1).1/2x+(-3/2x+1/3y^2)-(2x-2/3y^2),其中x=-1/3,y=2/3
(2).[(xy+2)(xy-2)-2x^2y^2+4]÷(xy),其中x=10,y=-1/25
(3).x(x+2y)-(x+1)^2+2x,其中x=1/25,y=-25

答案

(1).1/2x+(-3/2x+1/3y^2)-(2x-2/3y^2),其中x=-1/3,y=2/3
=1/2x-3/2x+1/3y^2-2x+2/3y^2
=-3x+y^2
=-3*(-1/3)+(2/3)^2
=1+4/9
=13/9
(2).[(xy+2)(xy-2)-2x^2y^2+4]÷(xy),其中x=10,y=-1/25
=(x^2y^2-4-2x^2y^2+4)÷(xy)
=-x^2y^2÷(xy)
=-xy
=-10*(-1/25)
=2/5
(3).x(x+2y)-(x+1)^2+2x,其中x=1/25,y=-25
=x^2+2xy-x^2-2x-1+2x
=2xy-1
=2*(1/25)*(-25)-1
=-2-1
=-3