tính tổng: \(B=\frac{5}{18\cdot21}+\frac{5}{21\cdot24}+\frac{5}{24\cdot27}+...+\frac{5}{123\cdot126}\)
tính tổng: Q=\(\dfrac{5}{18\cdot21}+\dfrac{5}{21\cdot24}+\dfrac{5}{24\cdot27}+...+\dfrac{5}{123\cdot126}\)
B=5/18*21+5/21*24+5/24*27+...+5/123*126
3/5B=3/5(5/18*21+5/21*24+...+5/123*126)
3/5B=3/5*5/18*21+3/5*5/21*24+...+3/5*5/123*126
3/5B=3/18*21+3/21*24+...+3/123*126
3/5B=1/18-1/21+1/21-1/24+...+1/123-1/126
3/5B=1/18-1/126
3/5B=126/2268-18/2268
3/5B=108/2268
3/5B=21
B=21÷3/5
B=21*5/3
B=35
Tính giá trị của biểu thức:
\(\frac{-3}{5}+\frac{28\cdot43}{5\cdot56}+\frac{28\cdot5}{5\cdot24}-\frac{28\cdot21}{5\cdot63}\)
\(=\)\(\frac{-3}{5}\)\(+\frac{28.43}{5.28.2}\)\(+\frac{4.7.5}{5.4.6}\)\(+\frac{28.21}{5.21.3}\)
\(=\)\(\frac{-3}{5}\)\(+\frac{43}{10}+\frac{7}{6}+\frac{28}{15}\)
\(=\)\(\frac{-48}{90}+\frac{387}{90}+\frac{85}{90}+\frac{168}{90}\)
\(=\)\(\frac{592}{90}\)
\(=\)\(\frac{296}{45}\)
\(\frac{6}{15\cdot18}+\frac{6}{18\cdot21}+\frac{6}{21\cdot24}+...+\frac{6}{87\cdot90}\)
sai đề
Đáng lẽ hạng tử đầu tiên phải là \(\frac{6}{15.18}\)
giúp mình bài này với
\(\frac{6}{15\cdot18}+\frac{6}{18\cdot21}+\frac{6}{21\cdot24}+...+\frac{6}{87\cdot90}\)
đặt bt trên là A
\(\frac{1}{2}\)A=\(\frac{3}{15.18}+\frac{3}{18.21}+\frac{3}{21.24}+...+\frac{3}{87.90}\)
\(\frac{1}{2}\)A=\(\frac{1}{15}-\frac{1}{18}+\frac{1}{18}-\frac{1}{21}+\frac{1}{21}-....+\frac{1}{87}-\frac{1}{90}\)
\(\frac{1}{2}A=\frac{1}{15}-\frac{1}{90}\)
..... tự tính nhé
tính\(\frac{9^{4^{ }}\cdot27^5\cdot3^6\cdot4^4}{3^8\cdot8^{14}\cdot24\cdot3\cdot8^2}\)
\(\frac{5\cdot415\cdot9^9-4\cdot3^{20}\cdot8^9}{5\cdot2^9\cdot2^{19}-7\cdot2^{19}.27^6}\)
\(\frac{8^5\cdot24^4\cdot72^2}{16^{12}\cdot125^2\cdot94^4}\)
Câu 1 : \(1,321338308x10^{-4}\)
Câu 2 : \(1316,572106\)
Câu 3 : \(1,641302619x10^{-13}\)
Ủng hộ nhé,tớ đang âm.
Thực hiện phép tính
A=\(\frac{5}{12\cdot17}+\frac{35}{17\cdot18}-\frac{39}{18\cdot21}+\frac{30}{21\cdot72}\)
A= 1/18 nhé bạn
xin lỗi vì mình không viết cách làm..........
D=\(\frac{6}{15\cdot18}+\frac{6}{18\cdot21}+\frac{6}{21\cdot24}+...+\frac{6}{87\cdot90}\)
E=\(\frac{3^2}{8\cdot11}+\frac{3^2}{11\cdot14}+\frac{3^2}{14\cdot17}+...+\frac{3^2}{197\cdot200}\)
\(\frac{3}{9\cdot15}+\frac{3}{15\cdot21}+\frac{3}{21\cdot27}+.....+\frac{3}{99\cdot105}\)
=\(\frac{1}{2}\cdot\left(\frac{6}{9\cdot15}+\frac{6}{15\cdot21}+\frac{6}{21\cdot27}+...+\frac{6}{99\cdot105}\right)\)
=\(\frac{1}{2}\cdot\left(\frac{1}{9}-\frac{1}{15}+\frac{1}{15}-\frac{1}{21}+\frac{1}{21}-\frac{1}{27}+...+\frac{1}{99}-\frac{1}{105}\right)\)
=\(\frac{1}{2}\cdot\left(\frac{1}{9}-\frac{1}{105}\right)\)
=\(\frac{1}{2}\cdot\left(\frac{35}{315}-\frac{3}{315}\right)\)
=\(\frac{1}{2}\cdot\left(\frac{32}{315}\right)\)
=\(\frac{1\cdot16}{1\cdot315}\)
=\(\frac{16}{315}\)
a,\(\frac{1995\cdot1994-1}{1994+1996\cdot1995}\)b,\(\frac{864\cdot48-432\cdot96}{864\cdot48\cdot432}\)c,\(\frac{1414+1515+1616+1717+1818+1919}{20\cdot20+21\cdot21+22\cdot22+23\cdot23+24\cdot24+25\cdot25}\)
d,\(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+\frac{1}{15}+\frac{1}{21}+...+\frac{1}{3240}\)
Đây là những bài lớp 5+ vậy nên không làm theo kiểu lớp 5 được, cố gắng tìm bài đúng lớp nhé bạn (VNNLL cc)