1+2+3+...+100
=(100+1)x100:2
=101x100:2
=101x50
=5050
1+2+3+...+100=(100+1)x100÷2=101x100÷2=101x50=5050
1+2+3+4+...+100
=(100+1)x100:2
=101x100:2
=101x50
=5050.
1+2+3+...+100
=(100+1)x100:2
=101x100:2
=101x50
=5050
1+2+3+...+100=(100+1)x100÷2=101x100÷2=101x50=5050
1+2+3+4+...+100
=(100+1)x100:2
=101x100:2
=101x50
=5050.
S=1×2+2×3+3×4+4×5+...........+99×100
3S=1×2×3+2×3×(4-1)+3×4×(5-2)+4×5×(6-3)+............+99×100×(101-98)
3S=1×2×3+2×3×4-1×2×3+3×4×5-2×3×4+4×5×6-3×4×5+.............+99×100×101-98×99×100
3S=99×100×101
Tại sao 3S=99×100×101
Các bạn giải thích hộ mình với!
MÌNH CẢM ƠN MỌI NGƯỜI!
bài 1
A=1*2*3+2*3*4+3*4*5+...+99*100*101
B=1*3*5+3*5*7+...+95*97*99
C=2*4+4*6+..+98*100
D=1*2+3*4+5*6+...+99*100
E=1^2+2^2+3^2+...+100^2
G=1*3+2*4+3*5+4*6+...+99*101+100*102
H=1*2^2+2*3^2+3*4^2+...+99*100^2
I=1*2*3+3*4*5+5*6*7+7*8*9+...+98*99*100
K=1^2+3^2+5^2+...+99^2
Tính C=1/2-(1/3+2/3)+(1/4+2/4+3/4)-(1/5+2/5+3/5+4/5)+...+(1/100+2/100+...+99/100)
Tính tổng 100-(1+1/2+1/3+1/4+...+1/100)/1/2+2/3+3/4+....+99/100
S=1×2+2×3+3×4+4×5+...........+99×100
3S=1×2×3+2×3×(4-1)+3×4×(5-2)+4×5×(6-3)+............+99×100×(101-98)
3S=1×2×3+2×3×4-1×2×3+3×4×5-2×3×4+4×5×6-3×4×5+.............+99×100×101-98×99×100
3S=99×100×101
Tại sao 3S=99×100×101
Các bạn giải thích hộ mình với!
MÌNH CẢM ƠN MỌI NGƯỜI!
CMR:
a)1/10^2 +1/11^2+1/12^2+...+1/100^2 >3/4
b)1/2^2+1/3^2+1/4^2+...+1/100^2<99/100
c)1/2^2+1/3^2+1/4^2+...+1/100^2<3/4
chứng minh : 100- (1+1/2+1/3+1/4+...+1/100)=1/2+2/3+3/4+...+99/100
1. (1+1/2).(1+1/2^2).(1+1/2^3)....(1+1/2^100) < 3
2. 1/(5+1)+2/(5^2+1)+4/(5^4+1)+...+ 1024/(5^1024+1) <1/4
3. 3/(1!+2!+3!)+4/(2!+3!+4!)+...+100/(98!+99!+100!) <1/2
100-(1+1/2+1/3+1/4+...+1/100)
1/2+2/3+3/4+...+99/100
chứng minh
100-(1+1/2+1/3+1/4+....+1/100)=(1/2+2/3+3/4+....+99/100)
5tick