1.先化简,后求值.(1)(x-2y)(x+2y)-(x-2y)^2,其中x=-2,y=1/2.2.解下列方程或方程组:(1)(x-1)(1+x)-(x+2)(x-3)=2x-5(2) (2x+1)(y-2)=2xy,x-2y=4
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![1.先化简,后求值.(1)(x-2y)(x+2y)-(x-2y)^2,其中x=-2,y=1/2.2.解下列方程或方程组:(1)(x-1)(1+x)-(x+2)(x-3)=2x-5(2) (2x+1)(y-2)=2xy,x-2y=4](/uploads/image/z/14834099-11-9.jpg?t=1.%E5%85%88%E5%8C%96%E7%AE%80%2C%E5%90%8E%E6%B1%82%E5%80%BC.%EF%BC%881%EF%BC%89%EF%BC%88x-2y%29%28x%2B2y%29-%28x-2y%29%5E2%2C%E5%85%B6%E4%B8%ADx%3D-2%2Cy%3D1%2F2.2.%E8%A7%A3%E4%B8%8B%E5%88%97%E6%96%B9%E7%A8%8B%E6%88%96%E6%96%B9%E7%A8%8B%E7%BB%84%EF%BC%9A%EF%BC%881%EF%BC%89%EF%BC%88x-1%29%281%2Bx%29-%28x%2B2%29%28x-3%29%3D2x-5%282%29+%282x%2B1%29%28y-2%29%3D2xy%2Cx-2y%3D4)
1.先化简,后求值.(1)(x-2y)(x+2y)-(x-2y)^2,其中x=-2,y=1/2.2.解下列方程或方程组:(1)(x-1)(1+x)-(x+2)(x-3)=2x-5(2) (2x+1)(y-2)=2xy,x-2y=4
1.先化简,后求值.
(1)(x-2y)(x+2y)-(x-2y)^2,其中x=-2,y=1/2.
2.解下列方程或方程组:
(1)(x-1)(1+x)-(x+2)(x-3)=2x-5
(2) (2x+1)(y-2)=2xy,x-2y=4
1.先化简,后求值.(1)(x-2y)(x+2y)-(x-2y)^2,其中x=-2,y=1/2.2.解下列方程或方程组:(1)(x-1)(1+x)-(x+2)(x-3)=2x-5(2) (2x+1)(y-2)=2xy,x-2y=4
1(1) (x-2y)(x+2y)-(x-2y)^2
=x^2-4y^2-(x^2-4xy+4y^2)
=4xy-8y^2(将x=-2,y=1/2代入此式)
=-6
2(1) (x-1)(1+x)-(x+2)(x-3)=2x-5,先化简,得
x^2-1-(x^2-x-6)=2x-5即
x+5=2x-5
x=10
2(2) 将(2x+1)(y-2)=2xy化简得
y-4x=2即y=4x+2
将y=4x+2代入关系式x-2y=4中可得
x-2(4x+2)=4计算得出x=-8/7
则y=-18/7
(1)4xy-8y2 -6
(2) x2-1-x2+x+6=2x-5
x=10
(3)2xy-4x+y-2=2xy 4x-y=-2 x=-8/7
x-2y=4 y=-18/7
1(1)是-16
1.原式=(X-2Y)(X+2Y-X+2Y)<提公因式>=4Y(X-2Y) 把X=-2,Y=1/2代入得;原式=-6. 2.(1)答案为10. (2)答案为;X=-8/7,Y=-18/7
1.(x-2y)(x+2y)-(x-2y)(x-2y)
(x-2y)(x+2y-x+2y)
(x-2y)4y
4xy-8y^2
4*2*1/2-8*1/2^2
2
这是第一个,等等帮你做下面的
2 (1)
(x-1)(x+1)-(x^2-3x+2x-6)=2x-5
x^2-1-x^2+x+6=2x-5
x+5=2x-5
x=10
2xy-4x+y-2=2xy,x=4+2y
y-4x=2
x=(y-2)/4
=4+2y
y-2=16+8y
y=-18/7
1.原式=x^2-4y^2-(x^2-4xy+4y^2)
=4xy-8y^2
=4*0.5*(-2)-8*0.5*0.5
=-6
2.(1) (x^2-1)-(x^2-x-6)=2x-5
x=10
(2)2xy+y-4x-2=2xy 得 y-4x=2
x-2y=4 得 x=-8/7
y=-18/7