Biết \(\frac{7}{15}<\frac{a}{40}<\frac{8}{15}\)
Tập hợp các số nguyên a thích hợp là ?
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Những câu hỏi liên quan
3 tháng 12 2017
a, (x-15):5+22=24
( x - 15 ) : 5 = 2
x-15 = 10
x = 25
QT
3
27 tháng 5 2018
\(2009-\left(4\frac{5}{9}+x-7\frac{7}{8}\right):15\frac{3}{2}=2008\)
\(\Leftrightarrow2009-\left(\frac{41}{9}+x-\frac{63}{8}\right):\frac{33}{2}=2008\)
\(\Leftrightarrow2009-\left(x-\frac{239}{72}\right):\frac{33}{2}=2008\)
\(\Leftrightarrow2009-\frac{2x}{33}+\frac{239}{1188}=2008\)
\(\Leftrightarrow\frac{-2x}{33}=\frac{-1427}{1188}\)
\(\Leftrightarrow-2376x=-47091\)
\(\Leftrightarrow x=\frac{1427}{72}\)
LD
21 tháng 5 2017
\(=\frac{12}{15}.\left(\frac{2}{7}+\frac{3}{7}+\frac{1}{7}+\frac{1}{7}\right)\)
\(=\frac{12}{15}.1\)
\(=\frac{12}{15}=\frac{4}{5}\)
T
3
31 tháng 3 2015
\(\frac{7}{15}=\frac{56}{120};\frac{8}{15}=\frac{64}{120};\frac{a}{40}=\frac{3a}{120}\)
\(\Rightarrow\frac{56}{120}
8 tháng 6 2023
\(\dfrac{1}{3\times7}+\dfrac{1}{7\times11}+\dfrac{1}{11\times15}+...+\dfrac{1}{a\times\left(a+4\right)}=\dfrac{50}{609}\)
\(\dfrac{1}{4}\times\left(\dfrac{4}{3\times7}+\dfrac{4}{7\times11}+...+\dfrac{4}{a\times\left(a+4\right)}\right)=\dfrac{50}{609}\)
\(\dfrac{1}{3}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{11}+...+\dfrac{1}{a}-\dfrac{1}{a\times4}=\dfrac{50}{609}\div\dfrac{1}{4}\)
\(\dfrac{1}{3}-\dfrac{1}{a\times4}=\dfrac{200}{609}\)
\(\dfrac{1}{a\times4}=\dfrac{1}{3}-\dfrac{200}{609}\)
\(\dfrac{1}{a\times4}=\dfrac{1}{203}\)
\(a\times4=203\)
\(a=\dfrac{203}{4}\)
NT
Nguyễn Thị Thương Hoài
Giáo viên
VIP
8 tháng 6 2023
\(\dfrac{1}{3\times7}\)+\(\dfrac{1}{7\times11}\)+\(\dfrac{1}{11\times15}\)+...+\(\dfrac{1}{a\times\left(a+4\right)}\) = \(\dfrac{50}{609}\)
4\(\times\)( \(\dfrac{1}{3\times7}\) +\(\dfrac{1}{7\times11}\)+\(\dfrac{1}{11\times15}\)+...+\(\dfrac{1}{a\times\left(a+4\right)}\)) = \(\dfrac{50}{609}\) \(\times\)4
\(\dfrac{4}{3\times7}\)+ \(\dfrac{4}{7\times11}\)+\(\dfrac{1}{11\times15}\)+...+\(\dfrac{4}{a\times\left(a+4\right)}\) = \(\dfrac{50}{609}\) \(\times\) 4
\(\dfrac{1}{3}\) - \(\dfrac{1}{7}\) + \(\dfrac{1}{7}\) - \(\dfrac{1}{11}\) + \(\dfrac{1}{11}\)-\(\dfrac{1}{15}\)+...+\(\dfrac{1}{a}\)-\(\dfrac{1}{a+4}\) = \(\dfrac{200}{609}\)
\(\dfrac{1}{3}\) - \(\dfrac{1}{a+4}\) = \(\dfrac{200}{609}\)
\(\dfrac{1}{a+4}\) = \(\dfrac{1}{3}\) - \(\dfrac{200}{609}\)
\(\dfrac{1}{a+4}\) = \(\dfrac{1}{203}\)
a + 4 = 203
\(a\) = 203 - 4
\(a\) = 199
Đáp số: \(a\) = 199
TM
4
16 tháng 3 2018
(\(\frac{15}{22}\)-\(\frac{7}{13}\)) x \(\frac{13}{7}\)- \(\frac{15}{22}\) x(\(\frac{6}{7}\)- \(\frac{22}{15}\))
=(\(\frac{15}{22}\)x \(\frac{13}{7}\)- 1) - \(\frac{15}{22}\)x\(\frac{6}{7}\)-1
=\(\frac{15}{22}\)x \(\frac{13}{7}\)-\(\frac{15}{22}\)x\(\frac{6}{7}\)(vì -1+1=0)
=\(\frac{15}{22}\)x(\(\frac{13}{7}\)-\(\frac{6}{7}\))
=\(\frac{15}{22}\)
làm hơi tắt nha
NT
16 tháng 3 2018
\(\left(\frac{15}{22}-\frac{7}{13}\right).\frac{13}{7}-\frac{15}{22}.\left(\frac{6}{7}-\frac{22}{15}\right)\)
\(=\frac{15}{22}.\frac{13}{7}-\frac{7}{13}.\frac{13}{7}-\frac{15}{22}.\frac{6}{7}+\frac{15}{22}.\frac{22}{15}\)
\(=\frac{15}{22}.\left(\frac{13}{7}-\frac{6}{7}\right)-1+1\)
\(=\frac{15}{22}.1-1+1\)
\(=\frac{15}{22}-\left(1-1\right)\)
\(=\frac{15}{22}-0\)
\(=\frac{15}{22}\)
30 tháng 3 2020
\(\frac{3}{7}\cdot15\cdot\frac{1}{3}+\frac{3}{7}\cdot5\cdot\frac{2}{5}\le x\le\left(3\frac{1}{2}:7-6\frac{1}{2}\right)\cdot\left(-2\frac{1}{3}\right)\)
\(\Leftrightarrow\frac{15}{7}+\frac{6}{7}\le x\le-6\cdot\frac{-5}{3}\)
\(\Leftrightarrow3\le x\le10\)
Mà \(x\in Z\)
\(\Rightarrow x\in\left\{4;5;6;7;8;9\right\}\)