先化简再求值 (1-x 2分之一)除以
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4分之一(-4x^2+2x-8)-(2分之一x-1)=1/4*(-4*1/4+2*1/2-8)-(1/2*1/2-1)=1/4*(-8)-(-3/4)=-2+3/4=-5/4
因为x^2=x+1,所以x^2-1=x两边平方有:(x^2-1)^2=x^4-2x^2+1=x^2则:x^4+1=3x^2所以x^2+1/x^2=(1+x^4)/x^2=3x^2/x^2=3
原式=(x+1)²/(x+2)÷(x+1)(x-1)/(x-1)-x/(x+2)=(x+1)²/(x+2)÷(x+1)-x/(x+2)=(x+1)/(x+2)-x/(x+2)=(x
先化简再求值(1/2a+1/3b)(1/3b-1/2b)-(1/3b-1/2a)^2+(-1/3b-1/2a)^2,其中a=1/2,b=-1/3(1/2a+1/3b)(1/3b-1/2a)-(1/3b
1,a平方加2ab加b平方可以写成完全平方式:(a+b)平方2,然后相乘:得(a+b)平方分之(a分之一加b分之一)乘以ab3,(a+b)平方分之(a分之一加b分之一)乘以ab=(a+b)平方分之a+
原式=9x+6x2-3x+2x2=8x2+6x,当x=-1时,原式=8×(-1)2+6×(-1)=8-6=2.
2a²-【二分之一(ab--4a²)+8ab】-二分之一ab=2a²-(二分之一ab-2a²+8ab)-二分之一ab=2a²-二分之一ab+2a&su
原式=-x2-y2-3xy-x2+y2=-2x2-3xy,当x=-1,y=2时,原式=-2×(-1)2-3×(-1)×2=4.
配方:1+x-x^2=5/4-(x-1/2)^2,套用不定积分公式(∫dx/√(a^2-x^2))结果是arcsin((2x-1)/√5)+C
(1-1/2^2)(1-1/3^2)(1-1/4^2).(1-1/2007^2)(1-1/2008^2)=(1-1/2)(1+1/2)(1-1/3)(1+1/3)(1-1/4)(1+1/4).(1-1
(x^2-2x+1)/(x^2-1)+1/(x+1)=(x-1)^2/(x+1)(x-1)+1/(x+1)=(x-1)/(x+1)+1/(x+1)=x/(x+1)=1-根2分之一
x²-3x+2=0(x-1)(x-2)=0因为分母x-1≠0所以x-2=0x=2原式=x(x-1)/(x-1)*(x+1)(x-1)/(x-1)²=x*(x+1)/(x-1)=2*
[(x-4)/(x^2-1)]÷[(x^2-3x-4)/(x^2+2x+1)]+1/(x-1)=[(x-4)/(x-1)(x+1)]÷[(x+1)(x-4)/(x+1)^2]+1/(x-1)=[(x-
解原式=[(x+1)²/(x+2)]×[(x-1)/(x-1)(x+1)]-1/(x+2)=[(x+1)²/(x+2)]×1/(x+1)-1/(x+2)=(x+1)/(x+2)-1
14x^2-4x+1=0=>x^2+1=4x=>(x^2+1)^2=16x^2=>x^4+1=14x^2---------①x^2+(1/x^2)=(1/x^2)(x^4+1)----------②把
1/(x-3)+6/(9-x^2)=1/(x-3)+6/(3-x)(3+x)=(x+3-6)/(x-3)(x+3)=1/(x+3)=1/(-2)=-1/2
①x2+3=3(x+1)x2-3x=0x(x-3)=0解得:x1=0,x2=3.②4(3x+1)2=25(x-2)24(3x+1)2-25(x-2)2=0(6x+2+5x-10)(6x+2-5x+10
1x2分之一+2x3分之一+3x4分之一+.+2010x2011分之一=1-1/2+1/2-1/3+1/3-1/4+……+1/2010-1/2011=1-1/2011=2010/2011
原式=2x2-2xy-6x2+9xy-2x2+2x2-xy+y2=-2x2+5xy+2y2,当x=-1,y=-2时,原式=-2+10+8=16.