Tính tổng:a,E=1+3+6+...+4950
b,D=2+6+12+...+9900
Những câu hỏi liên quan
Tính tổng:a, E=1+3+6+...+4950
b, D=2+6+12+...+9900
a)E=1+3+6+...+4950
2E=1.2+3.2+6.2+...+4950.2
2E=2+6+12+...+9900
Ta có: Xét D=1.2+3.2+6.2+...+4950.2
3D=1.2.3+2.3.4-1.2.3+3.4.5-2.3.4+...+99.100.101-98.99.100
3D=99.100.101
D=333300
Thay D vào E ta được 2E=333300 => E=166650
b)B=1+3+6+12+...+9900
2B=1.2+3.2+6.2+12.2+...+9900.2
2B=2+6+12+24+...+19800
Ta có xét A=1.2+3.2+6.2+12.2+...+9900.2
3A=1.2.3+3.2.6-1.2.3+...100.2.3
3A=98.100.102
A=33320
ta thay A vào B; 2B=33320=>B=16660
Đúng 0
Bình luận (0)
Tính tổng: a, E=1+3+6+...+4950
b, D=2+6+12+...+9900
=(4950-1) cgia cho 2 +1=................................
Đúng 0
Bình luận (0)
tính tổng : E=1+3+6+...+4950
D=2+6+12+...+9900
Tính :
A = 1 . 2 + 2 . 3 + 3 . 4 + ... + 99 . 100
B = 1 . 3 + 2 . 4 + 3 . 5 + ... + 99 . 100
C = 1 . 4 + 2 . 5 + 3 . 6 + ... + 99 . 102
D = 4 + 12 + 24 + ... + 19404 + 19800
E = 1 + 3 + 6 + 10 + ... + 4851 + 4950
Các bạn nhớ ủng hộ cho
nhất sông núi nhé
Cảm ơn bạn
Đúng 0
Bình luận (0)
A = 1 . 2 + 2 . 3 + 3 . 4 + ... + 99 .100
3 . A = 1. 2 . 3 + 2 . 3 . 3 + 3 . 4 . 3 + ... + 99 . 100 . 3
3 . A = 1 . 2 . 3 + 2 . 3 . ( 4 - 1 ) + 3 . 4 . ( 5 - 2 ) + ... + 99 . 100 . ( 1001 - 998 )
3 . A = 1 . 2 . 3 + 2 . 3 . 4 - 1 . 2 . 3 + 3 . 4 . 5 - 2 . 3 . 4 + ... + 99 . 100 . 1001 - 998 . 99 . 100
3 . A = 99 . ( 100 . 10 )
A = ( 99 . 100 . 10 ) : 3
A = 33000
Đúng 0
Bình luận (0)
\(A=\frac{7}{6}+\frac{13}{12}+\frac{21}{20}+\frac{31}{30}+...+\frac{9901}{9900}\)
\(B=\frac{2}{3}+\frac{5}{6}+\frac{9}{10}+\frac{14}{15}+...+\frac{4949}{4950}\)
\(A=\frac{7}{6}+\frac{13}{12}+\frac{21}{20}+...+\frac{9901}{9900}=\left(1+\frac{1}{2.3}\right)+\left(1+\frac{1}{3.4}\right)+\left(1+\frac{1}{4.5}\right)+...+\left(1+\frac{1}{99.100}\right)\)\(=\left(1+1+1+...+1\right)+\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{99.100}\right)\)
\(=98+\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{99}-\frac{1}{100}\right)=98+\left(\frac{1}{2}-\frac{1}{100}\right)\)
\(=98+\frac{49}{100}=98\frac{49}{100}\)
Đúng 0
Bình luận (0)
a/ 1/2 + 5/6 + 11/12 + 19/20
b/ 1/2 + 5/6 + 11/12 + 19/20 + 29/30 + 41/42
c/ (1-1/3) + (1-1/15) + (1-1/35) + (1-1/63)
d/ 1/2 + 5/6 + 11/12 + ... + 9899/9900
e/ 2/3 + 14/15 + 34/35 +62/63
f/ 2/3 + 14/15 + 34/35 + ... + 9998/9999
cái này tính cái gì thế
ko hiểu
tÍNH D = 2 + 6 + 12 + ... + 9900
Tính B=1/2+1/6+1/12+1/20+1/30+...+1/9900
Tính:
a, 5/12+(7/59+7/12)
b,(7/30+5/16)+(1/16-7/30)
c,3/5x9+3/9x13+3/13x17+...........+3/2013-2017
d,(7/1234+51/9781-5/2018)x(3/5+1/12-37/60)
e,1/3+1/6+1/10+.........+1/4950
g,5932+6001x5931/5932x6001-69
a. 5/12+(7/59+7/12)
=5/12+497/708
=66/59
b.(7/30+5/16)+(1/16-7/30)
=131/240+(-41/240)
=3/8
Đúng 0
Bình luận (0)
a) \(\frac{5}{12}+\left(\frac{7}{59}+\frac{7}{12}\right)\)
\(=\frac{5}{12}+\frac{7}{59}+\frac{7}{12}\)
\(=\left(\frac{5}{12}+\frac{7}{12}\right)+\frac{7}{59}\)
\(=1\frac{7}{59}\)
b) \(\left(\frac{7}{30}+\frac{5}{16}\right)+\left(\frac{1}{16}-\frac{7}{30}\right)\)
\(=\frac{7}{30}+\frac{5}{16}+\frac{1}{16}-\frac{7}{30}\)
\(=\frac{6}{16}=\frac{3}{8}\)
c) \(\frac{3}{5.9}+\frac{3}{9.13}+\frac{3}{13.17}+...+\frac{3}{2013.2017}\)
\(=\frac{3}{4}\left(\frac{1}{5}-\frac{1}{9}+\frac{1}{9}-\frac{1}{13}+\frac{1}{13}-\frac{1}{17}+...+\frac{1}{2013}-\frac{1}{2017}\right)\)
\(=\frac{3}{4}\left(\frac{1}{5}-\frac{1}{2017}\right)\)
\(=\frac{1509}{10085}\)
Đúng 0
Bình luận (0)