1/2+(1/3+2/3)+(1/4+2/4+3/4)+…+(1/50+2/50+3/50+…+48/50+49/50).
问题描述:
+(1 2
+1 3
)+(2 3
+1 4
+2 4
)+…+(3 4
+1 50
+2 50
+…+3 50
+48 50
).49 50
答
原式=
+1 2
+1+2 3
+…+1+2+3 4
=1+2+…+49 50
+1 2
+2 2
+…+3 2
=49 2
=1+2+…+49 2
.1225 2