不妨将每两项看做一个数,即a1=1/2,a2=1/8=(1/2)^3,a3=1/32=(1/2)^5……an就是一个首项为1/2,公比为1/4的等比数列.an=1/2×1/4^(n-1);Sn=1/2(1-1/4^n)/(1-1/4) =2/3*(1-1/4^n)
把n换成5就是答案.
1-1/2+1/4-1/8+1/16-1/32+1/64-1/128+1/256-1/512=s5=2/3*(1-1/4^5)=0.666015625
1-1/2+1/4-1/8+1/16-1/32+1/64-1/128+1/128+1/256-1/512
1个回答
相关问题
-
1+1?2+2?4+4?8+8?16+16?32+32 64+64 128+128 256+256 512+512 10
-
2/1+4/1+8/1+16/1+32/1+64/1+128/1+256/1+512/1+1024/1=?
-
2\1+4\1+8\1+16\1+64\1+128\1+256\1+512\1
-
计算1/2+1/4+1/8+1/16+1/32+1/64+1/128+1/256+1/512+1/1024
-
1/2+1/4+1/8+1/16+1/32+1/64+1/128+1/256
-
1/2-1/4-1/8-1/16-1/32-1/64-1/128-1/256
-
1/2+1/4+1/8+1/16+1/32+1/64+1/128+1/256=?
-
1/2-1/4-1/8-16/1-32/1-64/1-128/1-256/1
-
1/2+1/4+1/8+1/16+1/32+1/64+1/128+1/256
-
1+1/2+1/4+1/8+1/16+1/32+1/64+1/128+1/256+1/512最接近下面那个数字