数学问题
若f(x)=(x-2)(x-1)(x-3)(x-4)(x-5)则f`(3)等于(即求f(3) 的导数)
若f(x)=(x-2)(x-1)(x-3)(x-4)(x-5)则f`(3)等于(即求f(3) 的导数) f(x)=(x-2)(x-1)(x-3)(x-4)(x-5) 可以用乘积形式的求导法则,可以看出对(x-2)、(x-1)、(x-4)、(x-5)求导都有(x-3)项, 则对x=3其值均为0, 所以减少运算量,只对(x-3)项求导 f`(3)=(x-2)(x-1)(x-4)(x-5) [x=3] =4
f(x)=(x-2)(x-1)(x-3)(x-4)(x-5) 则lnf(x)=ln(x-1)+ln(x-2)+ln(x-3)+ln(x-4)+ln(x-5) 取导数: f'(x)/f(x)=1/(x-1)+1/(x-2)+1/(x-3)+1/(x-4)+1/(x-5) --->f'(x)=f(x)[1/(x-1)+1/(x-2)+1/(x-3)+1/(x-4)+1/(x-5)] =(x-2)(x-3)(x-4)(x-5)+(x-1)(x-3)(x-4)(x-5) +(x-1)(x-2)(x-4)(x-5)+(x-1)(x-2)(x-3)(x-5) +(x-1)(x-2)(x-3)(x-4) --->f'(3)=0+0+2*1(-1)(-2)+0+0 =4.
答:设g(x)=(x-1)(x-2)(x-3)(x-4)(x-5) f(x)=xg(x) f'(x)=g(x)+xg'(x) f'(0)=g(0)+0=g(0)=-...详情>>
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