TÍNH bằng cách hợp lí
a) A=\(\frac{44.66+34.41}{3+7+11+...+79}\)
b) B=\(\frac{1+2+3+.....+200}{6+8+10+....+34}\)
c) C=\(\frac{1.5.6+2.10.12+4.20.24+9.45.54}{1.3.5+2.6.10+4.12.20+9.27.45}\)
Các bạn giải hộ mình
Chú ý: vd: 44.66 +34.41 là phép nhân
3+7+11+.....+79 dấu ..... ko phải là phép nhân
Cảm ơn các bạn rất nhìu
2. tìm x
a. \(\dfrac{x}{8}\)=\(\dfrac{-9}{6}\)
b. \(\dfrac{4}{9}\)+\(\dfrac{7}{3}\):x=\(\dfrac{1}{5}\)
c. \(\dfrac{-5}{9}\)- x=\(\dfrac{4}{3}\)
d. x +\(\dfrac{4}{17}\)=\(\dfrac{2}{34}\)
e. \(\dfrac{3}{4}\).x=\(\dfrac{7}{8}\)
f. \(5\dfrac{4}{7}\): x=11
3. tính
a. \(\dfrac{1}{3}\)-\(\dfrac{6}{13}\).\(\dfrac{-9}{10}\).\(\dfrac{-13}{36}\)
b.\(\dfrac{-1}{3}\).\(\dfrac{-15}{7}\). \(\dfrac{34}{45}\)
cho A=\(\dfrac{1}{2}.\dfrac{3}{4}.\dfrac{5}{6}.\dfrac{7}{8}...\dfrac{79}{80}\)
CMR A<\(\dfrac{1}{9}\)
4, so sánh A và B:
a,A=\(\dfrac{3}{8^3}+\dfrac{7}{8^4}\);B=\(\dfrac{7}{8^3}+\dfrac{3}{8^4}\)
b,A=\(\dfrac{10^7+5}{10^7-8}\);B=\(\dfrac{10^8+6}{10^8-7}\)
c,A=\(\dfrac{10^{1992}+1}{10^{1991}+1}\);B=\(\dfrac{10^{1993}+1}{10^{1992}+1}\)
\(\text{Thực hiện phép tính một cách hợp lý nhất (nếu có thể):}\)
\(1\)) \(\left(\dfrac{-8}{13}:\dfrac{3}{7}+\dfrac{-5}{13}:\dfrac{3}{7}\right).\dfrac{\left(-4\right)^3.\left|-3\right|}{7}\)
\(2\)) \(75\)\(\text{%}\)\(-\left(\dfrac{5}{2}+\dfrac{5}{3}\right)+\left(-\dfrac{1}{2}\right)^2\)
1: \(\dfrac{1}{2}\cdot\left(1+2\right)+\dfrac{1}{3}\cdot\left(1+2+3\right)+\dfrac{1}{4}\cdot\left(1+2+3+4\right)+...+\dfrac{1}{2017}\cdot\left(1+2+3+...+2017\right)\)
2: tính hợp li
a, \(44\cdot82-20^2+18\cdot44\)
b, \(\left(6^{10}:6^8\right):\left\{780:\left[78\cdot5-\left(125\cdot7^2\right)+13\cdot5\right]\right\}\)
Bài 1: tính
Cho A= \(\dfrac{1}{31}+\dfrac{1}{32}+\dfrac{1}{33}+........+\dfrac{1}{60}>\dfrac{7}{12}\)
B=\(\dfrac{1}{3^2}+\dfrac{1}{3^2}+\dfrac{1}{5^2}+.....+\dfrac{1}{50^2}\)
CMR B > \(\dfrac{1}{4}\); B < \(\dfrac{4}{9}\)
C = \(\dfrac{1}{2}.\dfrac{3}{4}.\dfrac{5}{6}.\dfrac{7}{8}...........\dfrac{79}{80}\)<\(\dfrac{1}{9}\)
RÚT GỌN
\(a,\dfrac{121.75.130.169}{39.60.11.198}\)
\(b,\dfrac{\left(3.4.2^{16}\right)^2}{11.2^{13}.4^{11}.16^9}\)
\(c,\dfrac{5.\left(2^2.3^2\right)^9.\left(2^2\right)^6-2.\left(2^2.3\right)^{14}.3^6}{5.2^{28}.3^{19}-7.2^{29}.3^{18}}\)
TÍNH HỢP LÍ
\(a,\left(10^2+11^2+12^2\right):\left(13^2+14^2\right)\)
TÍNH NHANH
\(a,13-12+11+10-9+8-7-6+-4+3+2-1\)