tinh tong
S = 1 + 3 + 5 + ...+ 99
A = 1 + 2 + 3 + ...+100
B = 2 + 4 + 6 + ..+ 2016
*chu y : neu quy luat
tinh tong :S=1-2+3-4+5-6+...+2015-2016
S= 1-2 + 3-4 + 5-6+... ..+2015-2016(có 2016 số)
=(1-2) + (3-4) + (5-6) +...+(2015-2016) (có 2016:2=1008 nhóm có 2 số)
=-1 +(-1) +(-1) +...+(-1)( có 1008 số(-1))
=-1.1008
=-1008
vậy S=-1008
1. Neu quy luat roi cong them 3 so trong day so sau:1,2,3,6,11,20.
2. Neu quy luat roi tinh so thu 12 trong 2 day so sau:
a,3,6,11,18
b,3,8,15,24
Bai 4:Cho day so co quy luat sau:
a1=1+2
a2=3+4+5
a3=6+7+8+9
a4=10+11+12+13+14
a,Tim a100
b,Tinh tong a1+a2+...+a100
tinh tong S = 1-2+3-4+...+2016-2016
Vậy mình nói thảng nhé. Đề này sai số rồi.
Đề đúng như thế này mới hợp lí chứ:
S = 1-2+3-4+...+2015-2016
S= (1-2)+ (3-4) +...+ (2015-2016)
S= (-1)+ (-1)+...+ (-1)
S có 2016 số hạng => Có 1008 số (-1)
=> S= 1008. (-1) =-1008
Vậy S= -1008
A1/2+1/3+1/4+1/5+......+1/2015+1/2016
a,ting tong
b,neu cachbo 1 p/s nhung van bang A
Tinh tong S=1/1×2+1/2×3+1/3×4+...+1/2014×2015+1/2015×2016
\(S=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+....+\frac{1}{2015.2016}\)
\(S=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{2015}-\frac{1}{2016}\)
\(S=1-\frac{1}{2016}=\frac{2015}{2016}\)
\(S=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-........+\frac{1}{2015}-\frac{1}{2016}\)
\(S=\frac{1}{1}-\left(-\frac{1}{2}+\frac{1}{2}\right)+\left(-\frac{1}{3}+\frac{1}{3}\right)+......+\left(-\frac{1}{2015}+\frac{1}{2015}\right)-\frac{1}{2016}\)
\(S=\frac{1}{1}-\frac{1}{2016}=\frac{2015}{2016}\)
bai1:tinh tong S=1.3+3.5+5.7+...+99.101
bai2 :tinh tong S=1.4+4.7+7.10+...+2017.2020
bai 3: tinh tong N=2.4+4.6+6.8+..+100.102
bai 4: tinh tóng=2.6+6.10+10.14+14.18+...+42.46+50.54
bai 5:tinh tongB=2^2+4^2+6^2+...+100^2
bai 6:C=1^2+3^2+...+100^2
bai7: biet 1^2+2^2+3^2+...+10^2=385 tinh tong 2^2+4^2+6^2+...+20^2
bai 8: tinh tong s=1^2+2^2+3^2+...+99^2
Bài 1 :
\(S=1.3+3.5+5.7+...+99.101=3+15+35+...9999\)
Ta thấy :
\(3=2^2-1\)
\(15=4^2-1\)
\(35=6^2-1\)
.....
\(9999=100^2-1\)
\(\Rightarrow S=2^2+4^2+...+100^2-\left(1\right).\left(\left(100-2\right):2+1\right)\)
\(\Rightarrow S=\dfrac{100.\left(100+1\right)\left(2.100+1\right)}{6}-51\)
\(\Rightarrow S=\dfrac{100.101.201}{6}-51=338299\)
nhanh len nhé mik đang cần gấp ai lam trước mik tích cho
Bài 6 :
\(C=1^2+2^2+...+100^2=\dfrac{100.\left(100+1\right)\left(2.100+1\right)}{6}=\dfrac{100.101.201}{6}=338350\)
Bài 9 :
\(S=1^2+2^2+3^2+...+99^2=\dfrac{99.\left(99+1\right)\left(2.99+1\right)}{6}=\dfrac{99.100.199}{6}=328350\)
Tinh tong S=1/1×2+1/2×3+1/3×4+...+1/2014×2015+1/2015×2016
S = 1/1x2 + 1/2x3 + 1/3x4 + ... + 1/2014x2015 + 1/2015x2016
S = 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + ... + 1/2014 - 1/2015 + 1/2015 - 1/2016
S = 1 - 1/2016
S = 2015
\(S=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-......+\frac{1}{2015}-\frac{1}{2016}\)
\(S=\frac{1}{1}-\frac{1}{2016}=\frac{2015}{2016}\)
Tim chu so tan cung cua tong
1 x 2 + 2 x 3 + 3 x 4 + 4 x 5 + 5 x 6 + ...... + 2015 x 2016