因式分解(7x^2+5x)/(x^+1) - 5x/(x^2-6)

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因式分解(7x^2+5x)/(x^+1) - 5x/(x^2-6)

因式分解(7x^2+5x)/(x^+1) - 5x/(x^2-6)
因式分解(7x^2+5x)/(x^+1) - 5x/(x^2-6)

因式分解(7x^2+5x)/(x^+1) - 5x/(x^2-6)
原式=(7x^4-42x²+5x³-30x-5x³-5x)/(x²+1)(x²-6)
=(7x^4-42x²-35x)/(x²+1)(x²-6)
=7x(x³-6x-5)/(x²+1)(x²-6)
=7x(x³+x²-x²-6x-5)/(x²+1)(x²-6)
=7x[x²(x+1)-(x+1)(x-6)]/(x²+1)(x²-6)
=7x(x+1)(x²-x+6)/(x²+1)(x²-6)

5个数是a-2,a-1,a,a+1,a+2
则平均数是a
所以方差=[(a-2-a)²+(a-1-a)+(a-a)²+(a+1-a)²+(a+2-a)²]/5
=(4+1+0+1+4)/5
=2
所以标准差=√2