x4次方+8x²-9因式分解--------------------已知1/a+1/b=1/6,1/b+1/c=1/9,1/a+1/c=1/15,则abc/ab+ac+bc=-------

x4次方+8x²-9因式分解--------------------已知1/a+1/b=1/6,1/b+1/c=1/9,1/a+1/c=1/15,则abc/ab+ac+bc=-------
x4次方+8x²-9因式分解--------------------已知1/a+1/b=1/6,1/b+1/c=1/9,1/a+1/c=1/15,则abc/ab+ac+bc=-------

x4次方+8x²-9因式分解--------------------已知1/a+1/b=1/6,1/b+1/c=1/9,1/a+1/c=1/15,则abc/ab+ac+bc=-------
1.
x^4+8x^2-9
=x^4-1+8x^2-8
=(x^2+1)(x^2-1)+8(x^2-1)
=(x+1)(x-1)(x^2+9)
2.
1/a+1/b=1/6
1/b+1/c=1/9
1/a+1/c=1/15
三式相加得：2(1/a+1/b+1/c)=1/6+1/9+1/15=31/90
即：1/a+1/b+1/c=31/180
通分得：(ab+bc+ca)/(abc)=31/180
所以(abc)/(ab+ac+bc)=180/31
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