2015广东 先化简,再求值:x x²-1 (1 1 x-1)
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原式=4(x+4)(x−4)•x−42+xx+4=2x+4+xx+4=x+2x+4;当x=3时,原式=57.
原式=2xy+x+3x(x−1)÷y(x2+2x−3)(x−1)2=2xy+x+3x(x−1)•(x−1)2y(x−1)(x+3)=3xy,当x=2+3,y=2-3时,原式=1(2+3)(2−3)=1
原式=5x2y+{xy-[5x2y-7xy2-12xy]-4x2y-xy}-7xy2=5x2y+{xy-5x2y+7xy2+12xy-4x2y-xy}-7xy2=5x2y+xy-5x2y+7xy2+1
先化简,再求值:【1/(x-y)】-【1/(x+y)】/【xy²/(x²-y²)】,其中x=√2+1,y=√2-1【1/(x-y)】-【1/(x+y)】/【xy²
原式=(x−2)(x+4)x(x+1)2÷(x−2)(x+4)x(x+1)=(x−2)(x+4)x(x+1)2×x(x+1)(x−2)(x+4)=1x+1,当x=-45时,原式=1−45+1=5.
原式=2x2+y2−x2−2y2x+y=x2−y2x+y=x-y,当x=2+1,y=22-2时,原式=2+1-22+2=-2+3.
(1x2+4x+4+1x2+2x)÷x+1x+2=[1(x+2)2+1x(x+2)]×x+2x+1=2(x+1)x(x+2)2×x+2x+1=2x(x+2),当x=3时,原式=23×(3+2)=215
(3x/x+1-x/x-1)+x-2/x的平方-1=(3x(x-1)-x(x+1))/(x+1)(x-1)+x-2/x^2-1=(3x^2-3x-x^2-x+x-2)/(x^2-1)=(2x^2-3x
=x²/(x-1)-1/(x-1)=(x²-1)/(x-1)=(x+1)(x-1)/(x-1)=x+1当x=0时原式=0+1=1
x−4x−2+4x2−4x+4÷xx−2=x−4x−2+4(x −2)2×x−2x=x(x−4)+4x(x−2)=x−2x,当x=2sin45°=2时,原式=2−22=1-2.
原式=1x+2−(x−2)2x(x−1)÷(x+1)(x−1)−3x−1=1x+2−(x−2)2x(x−1)•x−1(x+2)(x−2)=1x+2−x−2x(x+2)=2x2+2x,由x2+2x-4=
原式=2x+1÷4x(x+1)=2x+1×x(x+1)4=x2,当x=-2时,原式=-22=-1.
原式=(x+2)(x+3)x+3•x−3(x+2)(x−2)−1=x−3x−2−x−2x−2=−1x−2;当x=3时,原式=−13−2=2+3.
能不能先用()把每个分数括起来?
原式=x+8(x−2)2•x(x−2)x+3+1x−2•x(x−2)x+3=x(x+8)(x−2)(x+3)+x(x−2)(x−2)(x+3)=2x(x+3)(x−2)(x+3)=2xx−2,方程x2
2x2-5x+x2+4x-3x2-2=(2+1-3)x2+(-5+4)x-2=-x-2;将x=12代入上式,得原式=-12-2=-52.
原式=2x+4−4x+2•(x+2)(x−2)x2,=2x−4x,当x=1时,原式=-2.