搜狗做题网1/(x2+x)+1/(x2+3x+2)+1/(x2+5x+6)+1/(x2+7x+12)=4/21
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1/(x2+x)+1/(x2+3x+2)+1/(x2+5x+6)+1/(x2+7x+12)=4/21
x2是x的平方
x2是x的平方
1/(x2+x)+1/(x2+3x+2)+1/(x2+5x+6)+1/(x2+7x+12)
=1/x(x+1)+1/(x+1)(x+2)+1/(x+2)(x+3)+1/(x+3)(x+4)
=1/x-1/(x+1)+1/(x+1)-1/(x+2)+1/(x+2)-1/(x+3)+1/(x+3)-1/(x+4)
=1/x-1/(x+4)
=4/(x²+4x)=4/21
x²+4x-21=0
(x+7)(x-3)=0
x1=-7
x2=3
检验得x1=-7,x2=3是原方程的解
=1/x(x+1)+1/(x+1)(x+2)+1/(x+2)(x+3)+1/(x+3)(x+4)
=1/x-1/(x+1)+1/(x+1)-1/(x+2)+1/(x+2)-1/(x+3)+1/(x+3)-1/(x+4)
=1/x-1/(x+4)
=4/(x²+4x)=4/21
x²+4x-21=0
(x+7)(x-3)=0
x1=-7
x2=3
检验得x1=-7,x2=3是原方程的解
解方程：1/x2+x +1/x2+3x+2 +1/x2+5x+6 +1/x2+7x+12 +1/x2+9x+20=5/x
1/(x2+3x+2)+1/(x2+5x+6)+1/(x2+7x+12)=1/(x+4)
1/(x2+x)+1/(x2+3x+2)+1/(x2+5x+6)+1/(x2+7x+12)=4/21
(x2+3x+9)/(x2-27)+(6x)/(9x-x2)-(x-1)/(6+2x)
解方程：X2--1/8(X2+2X)+X2+2X/3(X2--1)=11
先化解,再求值：【1/(x2+3x+2)+1/(x2+5x+6)+1/(x2+7x+12)】/1/(x2+9x+20),
x2-5x+1=0则x2+x2/1
解方程 x2+x-1/(x2+x)=3/2
（x2+5x+4）2+2（x2+5x+4)2+1=(x2+.
解方程7/（x+x2）-3/（x-x2）=6/（x2-1）
解方程 2/(x2-x)+6/(1-x2)=7/(x2+x)
解方程2/x2+x+3/x2-x=4/x2-1