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1)\(\left(x-280\right):35=56.5\)
\(\left(x-280\right):35=280\)
\(x-280=280.35\)
\(x-280=9800\)
\(x=9800+280\)
\(x=10080\)
2) \(\left(x-128+20\right):192=0\)
\(\Rightarrow\left(x-148\right):192=0\)
\(\Rightarrow x-148=0\)
\(\Rightarrow x=0+148\)
\(\Rightarrow x=148\)
3) \(460+85.4=\left(x+200\right).4\)
\(\Rightarrow\left(x+200\right).4=460+340\)
\(\Rightarrow\left(x+200\right).4=800\)
\(\Rightarrow x+200=800:4=200\)
\(\Rightarrow x+200=200\)
\(\Rightarrow x=200-200=0\)
4) \(x+5.2-\left(32+16.3:16-15\right)=0\)
\(\Rightarrow x+10-\left(32+3-15\right)=0\)
\(\Rightarrow x+10-20=0\)
\(\Rightarrow x+10=20\)
\(\Rightarrow x=20-10=10\)
nha m.n
a) \(\frac{x}{3}=\frac{5}{y}\)
\(\Rightarrow3.5=x.y\)
Ta thấy \(3.5=15\) nên \(x\in\left\{-5;-3;3;5\right\}\)
\(y\in\left\{-5;-3;3;5\right\}\)
\(\dfrac{1}{3}-\dfrac{1}{12}-\dfrac{1}{20}-\dfrac{1}{30}-\dfrac{1}{42}-\dfrac{1}{56}-\dfrac{1}{72}-\dfrac{1}{90}-\dfrac{1}{110}=x-\dfrac{5}{13}\)
\(\dfrac{1}{3}\) - \(\dfrac{1}{3.4}\) - \(\dfrac{1}{4.5}\) - \(\dfrac{1}{5.6}\) - \(\dfrac{1}{6.7}\) - \(\dfrac{1}{7.8}\)- \(\dfrac{1}{8.9}\) - \(\dfrac{1}{9.10}\) - \(\dfrac{1}{10.11}\) = \(x\) - \(\dfrac{5}{13}\)
\(\dfrac{1}{3}\) - (\(\dfrac{1}{3.4}\) + \(\dfrac{1}{4.5}\) + \(\dfrac{1}{5.6}\) + \(\dfrac{1}{6.7}\)+ \(\dfrac{1}{7.8}\) + \(\dfrac{1}{8.9}\) + \(\dfrac{1}{9.10}\) + \(\dfrac{1}{10.11}\) =\(x\)-\(\dfrac{5}{13}\)
\(\dfrac{1}{3}\) - (\(\dfrac{1}{3}\) - \(\dfrac{1}{4}\) + \(\dfrac{1}{4}\) - \(\dfrac{1}{5}\) +...+ \(\dfrac{1}{9}\) - \(\dfrac{1}{10}\) + \(\dfrac{1}{10}\) - \(\dfrac{1}{11}\)) = \(x\) - \(\dfrac{5}{13}\)
\(\dfrac{1}{3}\) - (\(\dfrac{1}{3}\) - \(\dfrac{1}{11}\)) = \(x\) - \(\dfrac{5}{13}\)
\(\dfrac{1}{3}\) - \(\dfrac{1}{3}\) + \(\dfrac{1}{11}\) = \(x\) - \(\dfrac{5}{13}\)
\(x-\dfrac{5}{13}=\dfrac{1}{11}\)
\(x\) = \(\dfrac{1}{11}\) + \(\dfrac{5}{13}\)
\(x\) = \(\dfrac{68}{143}\)
a) \(3^x-27.3^5.3^2=0\)
\(3^x-3^3.3^5.3^3=0\)
\(3^x=3^{13}\)
\(x=13\)
b) \(\left(-5+3x\right):4=16\)
\(-5+3x=64\)
\(3x=69\)
\(x=23\)
(x-280):35= 56:5=56/5
x-280=56/5.35=392
x=392+280=672
( x - 280 ) : 35 = 56 : 5
( x - 280 ) : 35 = 11.2
x - 280 = 11.2 x 35
x - 280 = 392
x = 392 + 280
x = 672