Question

3x的平方-(2x的平方+5x-1)-(3x+1),其中x=20;(xy-3/2y-1/2)-(xy-3/2x+1,其中x=10/3,y=8/3;4y的平方-(x的...

3x的平方-(2x的平方+5x-1)-(3x+1),其中x=20;(xy-3/2y-1/2)-(xy-3/2x+1,其中x=10/3,y=8/3;4y的平方-(x的平方+y)+(x的平方-4y的平方)其中x=-28,y=18;做详细一点

Answer 1

3x²-(2x²+5x-1)-(3x+1)
=x²-5x+1-3x-1
=x²-8x
=20²-8*20
=240
(xy-3/2y-1/2)-(xy-3/2x+1)
=xy-3/2y-1/2-xy+3/2x-1
=3/2(x-y)-3/2
=3/2(10/3-8/3)-3/2
=-1/2
4y²-(x²+y)+(x²-4y²)
=-y
=-18
∴原式值为-18

Answer 2

晕····你化简一下不就得啦···还用问吗？？
3x2-(2x2+5x-1)-(3x+1)= x2-8x=20×20-8×20=240
(xy-3/2y-1/2) -(xy-3/2x+1)= -3/2y+3/2x-3/2=-y+x-1=-1/3
4y2-(x2+y)+(x2-4y2)=-y=-18

Answer 3

3x²-(2x²+5x-1)-(3x+1)
=x²-5x+1-3x-1
=x²-8x
=20²-8*20
=240
(xy-3/2y-1/2)-(xy-3/2x+1)
=xy-3/2y-1/2-xy+3/2x-1
=3/2(x-y)-3/2
=3/2(10/3-8/3)-3/2
=-1/2
4y²-(x²+y)+(x²-4y²)
=-y
=-18

Answer 4

拜托，你写的是算式吗？