化简[(2³-1)(3³-1)(4³-1)...(99³-1)(100³-1)]/[(2³+1)(3³+1)(4³+1)...(99³+1)(100&
问题描述:
化简[(2³-1)(3³-1)(4³-1)...(99³-1)(100³-1)]/[(2³+1)(3³+1)(4³+1)...(99³+1)(100³+1)]
其值最接近于()
A.1/2 B.1/3 C.2/3 D.5/8
另一题:分解因式:x^4 -x^3 +x^2+2
答
选C你可以设通项为(n^3-1)/(n^3+1),原式为n从2到100通项的乘积∏(n^3-1)/(n^3+1)=∏(n-1)[n(n+1)+1]/{(n+1)[(n-1)n+1]}=∏[(n-1)/(n+1)]*∏{[n(n+1)+1]/[(n-1)n+1]}={2/[n(n+1)]}{[n(n+1)+1]/(1*2+1)}=(2/3){[n(n+1)...