{3X-2T=4 2Y+T=3,则X与Y之间的关系式为?

网友回答

原式=[(a+2)/a(a-2)-(a-1)/(a-2)²][a(a-2)/(4-a)]
=[(a²-4-a²+1)/a(a-2)²][a(a-2)/(4-a)]
=-3/[(a-2)(4-a)]
=-3/(1*1)
=-3 (1/5)^n-2/5^(n+1)
=(1/5)^n-2/5*5^n
=(3/5)*(1/5)^n
所以limS2n=(a1+a2)+(a3+a4)+……
这是无穷等比递缩数列
所以=a1/(1-q)
=(3/25)/(1-1/5)=3/20