已知7/[A(上2下x+1)]=2/[A(上2下x)]+2/[A(上2下x-1)],求A(上2下x).ps:
问题描述:
已知7/[A(上2下x+1)]=2/[A(上2下x)]+2/[A(上2下x-1)],求A(上2下x).ps:
答
7/x(x+1)=2/x(x-1)+2/(x-1)(x-2)=[2(x-2)+2x]/[x(x-1)(x-2)]=4(x-1)/[x(x-1)(x-2)]=4/x(x-2)
所以:7/(x+1)=4/(x-2)
x=6.