1) Tính nhanh
a) A=\(\frac{3}{11\text{x}13}+\frac{3}{13\text{x}15}+\frac{3}{15\text{x}17}+...+\frac{3}{97\text{x}99}\)
b) B=\(\frac{4}{7\text{x}31}+\frac{6}{7\text{x}11}+\frac{9}{10\text{x}41}+\frac{7}{10\text{x}57}\)
3) Chứng tỏ phân số \(\frac{8n+5}{6n+4}\)tối giản với mọi số nguyên khác 0
a)\(\frac{-2}{3}.x+\frac{1}{5}=\frac{3}{10}\)
b )\(2\frac{7}{9}-\frac{12}{13}x=\frac{7}{9}\)
c)\(\text{|}x\text{|}-\frac{3}{4}=\frac{5}{3}\)
d) \(\frac{17}{2}-\text{|}2x-\frac{3}{4}\text{|}=-\frac{7}{4}\)
A=\(\frac{5x\left(2^2\text{x}3^2\right)^9\text{x}\left(2^2\right)^6-2\text{x}\left(2^2\text{x}3\right)^{14}\text{x}3^4}{\text{ }5\text{x}2^{28}\text{x}3^{18}-7\text{x}2^{29}\text{x}3^{18}}\)
\(\text{Tìm }x,\text{ }\text{biết:}\)
\(1\text{)}\text{ }2.\left(x-\frac{1}{3}\right)-3\left(x-\frac{1}{2}\right)=\frac{1}{2}x\)
\(2\text{) }-3\left(x-\frac{1}{4}\right)-\frac{1}{3}\left(x+\frac{1}{2}\right)=x\)
\(\text{3) }\frac{3}{2}\left(x-\frac{5}{3}\right)-\frac{4}{5}=x+1\)
\(\text{4) }\frac{1}{6}\left(2.x-3\right)=\frac{1}{2}\left(-x+\frac{1}{4}-\frac{2}{3}\right)\)
\(\text{5) }-\frac{2}{3}\left(x-\frac{1}{4}\right)=\frac{1}{3}\left(2.x-1\right)\)
B=\(\frac{0,18\text{x}1230+0,9\text{x}4567\text{x}2+3\text{x}5310\text{x}0,6}{1+4+7+10+...+55+58-410}\)
A=\(\frac{1\text{x}2+2\text{x}4+3\text{x}6+...+n\text{x}2n}{3\text{x}4+6\text{x}8+9\text{x}12+...+x}\)
Tính A biết:
\(A=\frac{1\text{x}2+2\text{x}4+3\text{x}6+...+n\text{x}2n}{3\text{x}4+6\text{x}8+9\text{x}12+...+x}\)
bai 1 \(\frac{-3}{\text{2}}+\frac{5}{7}+\frac{-31}{14}< hoac=\text{x}< \frac{1}{\text{2}}+\frac{1}{3}+\frac{1}{6}\)\(\frac{1}{6}\)
bai 2 \(\frac{\text{x}+4}{\text{x}-\text{2}}+\frac{\text{2}\text{x}-5}{\text{x}-\text{2}}\)la so nguyen
\(\frac{11}{40}+\frac{4}{5}-\text{|}\frac{3}{4}-1\frac{5}{12}\text{|}=\frac{3}{20}-x\)