tìm x, biết:
\(\frac{x}{49}=\frac{-2}{7}\)
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Tìm x biết \(\frac{1.2+2.3+3.4+...+98.99:49}{26950}.x=12+\frac{\frac{6}{7}}{\frac{-3}{2}}\)
Tìm x biết:
\(\frac{6^{x+3}-6^{x+1}+6^x}{211}=\frac{7^{2x}+7^{2x+1}+7^{2x-3}}{8\frac{1}{49}}\)
Tìm x, biết :
a, \(60\%x+0,4x+x:3=2\)
b, \(\left|2x-5\right|-7=\left(\frac{1}{49}-\frac{1}{3^2}\right)\left(\frac{1}{49}-\frac{1}{4^2}\right)...\left(\frac{1}{49}-\frac{1}{2015^2}\right)\)
c, \(\frac{x+1}{1}+\frac{2x+3}{3}+\frac{3x+5}{5}+...+\frac{20x+39}{39}=22+\frac{4}{3}+\frac{6}{5}+...+\frac{40}{39}\)
a. 60%x + 0,4x + x : 3 = 2
0.6x + 0,4x + x : 3 = 2
x(0,6 + 0,4 : 3 ) = 2
\(x.\frac{1}{3}=2=>x=2:\frac{1}{3}=\frac{1}{6}\)
câu B tự làm nha .
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Tìm x ,biết:
\(2-\left(\frac{37}{7}+x-3\right)\times\frac{49}{11}=0\)
\(2-\left(\frac{37}{7}+x-3\right)x\frac{49}{11}=0\)
\(\left(\frac{37}{7}+x-3\right)x\frac{49}{11}=2\)
\(\frac{37}{7}+x-3=\frac{22}{49}\)
\(x=-\frac{90}{49}\)
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\(2-\left(\frac{37}{7}+x-3\right)\cdot\frac{49}{11}=0\)
\(\left(\frac{37}{7}+x-3\right)\cdot\frac{49}{11}=0+2\)
\(\left(\frac{37}{7}+x-3\right)\cdot\frac{49}{11}=2\)
\(\frac{37}{7}+x-3=2:\frac{49}{11}\)
\(\frac{37}{7}+x-3=\frac{22}{49}\)
\(\frac{37}{7}+x=\frac{22}{49}+3\)
\(\frac{37}{7}+x=\frac{169}{49}\)
\(x=\frac{169}{49}-\frac{37}{7}\)
\(x=-\frac{90}{49}\)
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Tìm số tự nhiên x biết:
\(\frac{6^{x+3}-6^{x+1}+6^x}{211}=\frac{7^{2x}+7^{2x+1}+7^{2x-3}}{8\frac{1}{49}}\)
Tìm \(x,y,z\)biết : \(\frac{x}{7}=\frac{-y}{4}=-\frac{8}{z}=\frac{-28}{49}\)
\(\frac{x}{7}=\frac{-y}{4}=\frac{-8}{z}=\frac{-28}{49}\)
Cái này thì phải làm ngược từ phải sang trái =))
* \(\frac{-8}{z}=\frac{-28}{49}\Leftrightarrow-28z=-8\cdot49\Leftrightarrow-28z=-392\Leftrightarrow z=14\)
* \(\frac{-y}{4}=\frac{-8}{14}\Leftrightarrow-14y=-8\cdot4\Leftrightarrow-14y=-32\Leftrightarrow y=\frac{16}{7}\)
* \(\frac{x}{7}=\frac{-\frac{16}{7}}{4}\Leftrightarrow4x=-\frac{16}{7}\cdot7\Leftrightarrow4x=-16\Leftrightarrow x=-4\)
\(\frac{x}{7}=\frac{-y}{4}=\frac{-8}{z}=\frac{-28}{49}\)
\(\Rightarrow\frac{x}{7}=\frac{-28}{49};\frac{-y}{4}=\frac{-28}{49};\frac{-8}{z}=\frac{-28}{49}\)
+)\(\frac{x}{7}=\frac{-28}{49}\Rightarrow49x=\left(-28\right).7\Rightarrow49x=-196\Rightarrow x=\frac{-196}{49}=-4\)
+)\(\frac{-y}{4}=\frac{-28}{49}\Rightarrow-49y=\left(-28\right).4\Rightarrow-49y=-112\Rightarrow y=\frac{-112}{49}\)
+)\(\frac{-8}{z}=\frac{-28}{49}\Rightarrow-28z=49.\left(-8\right)\Rightarrow-28z=-392\Rightarrow z=\frac{-392}{-28}=14\)
Vậy x=-4;y=\(\frac{-112}{49}\);z=14
Chúc bạn học tốt
Tìm x và y : \(\frac{x+5}{-7}=\frac{5}{30-y}=\frac{7^2}{49}\)
\(\frac{7^2}{49}=1\)
\(\frac{x+5}{-7}=\frac{5}{30-y}=1\)
*\(\frac{x+5}{-7}=1\Rightarrow x=-12\)
*\(\frac{5}{30-y}=1\Rightarrow y=25\)
Vậy x = -12; y = 25
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Tìm x ,biết:
a)\(5x\):\(\frac{3}{5}=\frac{4}{7}:\sqrt{\frac{4}{49}}\)
b)\(0,15:3\sqrt{x}=0,3:\frac{2}{3}\)
a,\(\frac{25x}{3}=\frac{\frac{4}{7}}{\frac{2}{7}}=7\)=> x=\(\frac{21}{25}\)
b,\(\frac{0,15}{3\sqrt{x}}=\frac{0,3\cdot3}{2}\)<=>\(0,3=0,3\cdot9\sqrt{x}\)Hay \(\sqrt{x}=\frac{1}{9}=>x=\frac{1}{3}\)
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Tìm \(x\) biết:
a)\(\left|2x-5\right|-7=\left(\frac{1}{49}-\frac{1}{3^2}\right)\left(\frac{1}{49}-\frac{1}{4^2}\right).....\left(\frac{1}{49}-\frac{1}{2015^2}\right)\)
b)\(\frac{x+1}{1}+\frac{2x+3}{3}+\frac{3x+5}{5}+...+\frac{20x+39}{39}=22+\frac{4}{3}+\frac{6}{5}+...+\frac{40}{39}\)