Tìm x
7/3 - x = 11/5 : 5/6
x + 5/2 x 2/3 = 5/2
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Bài 1:
a: \(x=\dfrac{2}{3}:\dfrac{3}{5}=\dfrac{2}{3}\cdot\dfrac{5}{3}=\dfrac{10}{9}\)
b: \(x=\dfrac{17}{8}:\dfrac{7}{17}=\dfrac{17}{8}\cdot\dfrac{17}{7}=\dfrac{289}{56}\)
c: \(x=-\dfrac{3}{4}:\dfrac{7}{12}=\dfrac{-3}{4}\cdot\dfrac{12}{7}=\dfrac{-63}{28}=-\dfrac{9}{4}\)
d: \(\Leftrightarrow x\cdot\dfrac{1}{6}=\dfrac{3}{8}-\dfrac{1}{4}=\dfrac{1}{4}\)
hay \(x=\dfrac{1}{4}:\dfrac{1}{6}=\dfrac{3}{2}\)
e: \(\Leftrightarrow\dfrac{1}{2}:x=-4-\dfrac{1}{3}=-\dfrac{17}{3}\)
hay \(x=-\dfrac{1}{2}:\dfrac{17}{3}=\dfrac{-3}{34}\)
\(a,\dfrac{5}{8}=\dfrac{x}{14}\)
\(\Rightarrow x=\dfrac{5.14}{8}=8,75\)
Vậy \(x=8,75\)
\(b,\dfrac{x}{6}=-\dfrac{1}{3}\)
\(\Rightarrow x=-\dfrac{1.6}{3}=-2\)
Vậy \(x=-2\)
\(c,-\dfrac{3}{5}=\dfrac{x}{10}\)
\(\Rightarrow x=-\dfrac{3.10}{5}=-6\)
Vậy \(x=-6\)
câu d đã có đáp án
5^6+5^7+5^8
=5^6.(1+5+5^2)
=5^6.31 chia hết cho 31
7^6+7^5-7^4
=7^4.(7^2+7-1)
=7^4.55 chia hết cho 11
BÀI 2:
a) \(5^6+5^7+5^8=5^6\left(1+5+5^2\right)=5^6.31\) \(⋮\)\(31\)
b) \(7^6+7^5-7^4=7^4.\left(7^2+7-1\right)=7^4.55\)\(⋮\)\(11\)
c) \(2^3+2^4+2^5=2^3.\left(1+2+2^2\right)=2^3.7\)\(⋮\)\(7\)
d) mk chỉnh đề
\(1+2+2^2+2^3+...+2^{59}\)
\(=\left(1+2\right)+\left(2^2+2^3\right)+...+\left(2^{58}+2^{59}\right)\)
\(=\left(1+2\right)+2^2\left(1+2\right)+...+2^{58}\left(1+2\right)\)
\(=\left(1+2\right)\left(1+2^2+...+2^{58}\right)\)
\(=3\left(1+2^2+...+2^{58}\right)\)\(⋮\)\(3\)
\(a)x+\frac{2}{3}=\frac{5}{6}\)
\(x=\frac{5}{6}-\frac{2}{3}\)
\(x=\frac{5}{6}-\frac{4}{6}=\frac{1}{6}\)
\(b)x-\frac{3}{5}=\frac{2}{7}+\frac{1}{5}\)
\(x=\frac{3}{5}-\frac{17}{35}\)
\(x=\frac{21}{35}-\frac{17}{35}\)
\(x=\frac{4}{35}\)
\(c)x\div\frac{9}{11}=\frac{5}{22}\)
\(x=\frac{5}{22}\times\frac{9}{11}\)
\(x=\frac{45}{242}\)
\(d)\frac{3}{5}\times x=\frac{3}{10}\)
\(x=\frac{3}{10}\div\frac{3}{5}\)
\(x=\frac{1}{2}\)
\(a)\)\(x+\frac{2}{3}=\frac{5}{6}\)
\(x=\frac{5}{6}-\frac{2}{3}\)
\(x=\frac{1}{6}\)
\(b)\)\(x-\frac{3}{5}=\frac{2}{7}+\frac{1}{5}\)
\(x-\frac{3}{5}=\frac{17}{35}\)
\(x=\frac{17}{35}+\frac{3}{5}\)
\(x=\frac{38}{35}\)
a)x=-23/75
b)x=5/6