先化简,再求值1 x 2-x²-4x 4 x²-x
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原式=-x-2,当x=12时,原式=-12-2=-212.
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.
:(1)2x2-5x+x2+4x,其中x=-3=3x²-x=3x(-3)²+3=27+3=30(2)(3x2-xy-2y2)-2(x2+xy-2y2),其中x=6,y=-1=3x&
2x(3x2-4x+1)-3x2(2x-3),=6x3-8x2+2x-6x3+9x2,=x2+2x,当x=-3时,原式=(-3)2+2×(-3)=9-6=3.
原式=-x2+x(4分),当x=-1时,原式=-2.
(3x2-4x+5)(3x2+4x-5)-x2(9x2-16)=[3x2-(4x-5)][3x2+(4x-5)]-9x4+16x2=9x4-(4x-5)2-9x4+16x2=9x4-16x2+40x-
原式=9x+6x2-3x+2x2=8x2+6x,当x=-1时,原式=8×(-1)2+6×(-1)=8-6=2.
5x(x2+2x+1)-x(x-4)(5x-3)=5x3+10x2+5x-5x3+3x2+20x2-12x=33x2-7x,当x=1时,原式=33×12-7×1=26.
原式=-x2-3x+8x+2x2=x2+5x,当x=-2时,原式=4-10=-6.
原式=[x+2x(x-2)-x-1(x-2)2]÷x2-16x2+4x=[x2-4x(x-2)2-x2-xx(x-2)2]÷x2-16x2+4x=x-4x(x-2)2•x(x+4)(x+4)(x-4)
x²+2x+1=10(x+1)²=10x+1=3或x+1=-3所以x=2或x=-4【(x²+4)/x-4】÷【(x²-4)/(x²+2x)】=【(x&
原式=1-[(x)-1/(1-x)]²÷[(x²-x+1)/(x²-2x+1)]=1-[x(1-x)/(1-x)-1/(1-x)]²÷[(x²-x+1
原式=(x-1)(x+1)/(x+2)*(x+2)/x-1=x+1然后代入数值即可很高兴为您解答,【学习宝典】团队为您答题.请点击下面的【选为满意回答】按钮,
原式=(-x2+5x+4)+(5x-4+2x2)=-x2+5x+4+5x-4+2x2=x2+10x=x(x+10).∵x=-2,∴原式=-16.
原式={x(x-2)/[(x+1)(x-1)]}÷[(x-1)(x+1)/(x-1)-(2x-1)/(x+1)]={x(x-2)/[(x+1)(x-1)]}÷[(x²-1-2x+1)/(x+
x(x2-4)-(x+3)(x2-3x+2)-2x(x-2)=x3-4x-(x3-3x2+2x+3x2-9x+6)-2x2+4x=x3-4x-x3+3x2-2x-3x2+9x-6-2x2+4x=-2x
原式=x2-2x2+4y+2x2-2y=x2+2y,当x=-1,y=12时,原式=(-1)2+2×12=2.
x2-4x+3=0∴(x-3)(x-1)=0∵x-1≠0∴x-3=0∴x=3:(x2-3/x-1-2)除以1/x-1=(x²-3-2x+2)/(x-1)×(x-1)=x²-2x-1
(5x+2-x+2)÷x-32x2+4x=(5x+2-x-21)•2x(x+2)x-3=5-(x+2)(x-2)x+2•2x(x+2)x-3=-(x+3)(x-3)x+2•2x(x+2)x-3=-2x
原式=(x+1)/(x+1)²×x(x-1)/[-2(x-1)]=-1/(x+1)×x/2=-x/2(x+1)当x=√2时原式=-√2/2(√2+1)=-√2(√2-1)/2=(√2-2)/