Bài 2:Tìm x biết
a) \(\left(-0,6\right)^6.x=\left(\frac{-3}{5}\right)^8\)
b) \(\left(0,5-x\right)^3=-8\)
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KK
5 tháng 9 2021
a. (x - 22) - 1 = 0
<=> x - 4 - 1 = 0
<=> x = 5
b. 4 - (x - 2)2 = 0
<=> 22 - (x - 2)2 = 0
<=> (2 - x + 2)(2 + x - 2) = 0
<=> x(4 - x) = 0
<=> \(\left[{}\begin{matrix}x=0\\4-x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=4\end{matrix}\right.\)
KK
5 tháng 9 2021
d. (3x - 2)2 - (2x + 3)2 = 5(x + 4)(x - 4)
<=> (3x - 2 - 2x - 3)(3x - 2 + 2x + 3) = 5(x2 - 16)
<=> (x - 5)(5x + 1) = 5x2 - 80
<=> 5x2 + x - 25x - 5 = 5x2 - 80
<=> 5x2 - 5x2 + x - 25x = -80 + 5
<=> -24x = -75
<=> x = \(\dfrac{25}{8}\)
21 tháng 1 2017
a) \(\frac{3}{4}+\frac{1}{4}.x=\frac{1}{2}+\frac{1}{2}x\)
\(\Rightarrow3.\frac{1}{4}+\frac{1}{4}.x=\frac{1}{2}.\left(x+1\right)\)
\(\Rightarrow\frac{1}{4}.\left(x+3\right)=\frac{1}{2}.\left(x+1\right)\)
\(\Rightarrow\frac{x+1}{x+3}=\frac{1}{4}:\frac{1}{2}=\frac{1}{2}\)\(\Rightarrow\left(x+1\right).2=x+3\Rightarrow2x+2=x+3\)
\(\Rightarrow2x-x=3-2\Rightarrow x=1\)
vay x=1
9 tháng 8 2018
a) \(3^{7x-1}=815\)
\(\Leftrightarrow3^{7x}:3=815\)
\(\Leftrightarrow\left(3^7\right)^x:3=815\)
\(\Leftrightarrow2187^x=815.3\)
\(\Leftrightarrow2187^x=2445\)
\(\Rightarrow\) Không có x thoả mãn.
b) \(\left(-0,6\right)^5.x=\left(\dfrac{-3}{5}\right)^8\)
\(\Leftrightarrow x=\left(\dfrac{-3}{5}\right)^8:\left(-0,6\right)^5\)
\(\Leftrightarrow x=\left(-0,6\right)^8:\left(-0,6\right)^5\)
\(\Leftrightarrow x=\left(-0,6\right)^3\)
c) \(\left(0,5-x\right)^3=-8\)
\(\Leftrightarrow\left(0,5-x\right)^3=\left(-2\right)^3\)
\(\Rightarrow0,5-x=-2\)
\(\Leftrightarrow x=0,5+2\)
\(\Leftrightarrow x=2,5\).
18 tháng 12 2016
c) \(\frac{0,375-0,3+\frac{3}{11}+\frac{3}{12}}{0,625-0,5+\frac{5}{11}+\frac{5}{12}}=\frac{3\left(0,125-0,1+\frac{1}{11}+\frac{1}{12}\right)}{5\left(0,123-0,1+\frac{1}{11}+\frac{1}{12}\right)}=\frac{3}{5}\)
3 tháng 9 2015
a, \(\left(\frac{5}{8}.0,6-5:3\frac{1}{3}\right).\left(\frac{1}{5}-1,4\right).\left(-5\right)^2.x=120\)
\(\left(\frac{5}{8}.\frac{3}{5}-5:\frac{10}{3}\right)\left(\frac{1}{5}-\frac{7}{5}\right).25x=120\)
\(\left(\frac{3}{8}-\frac{3}{2}\right)\left(-\frac{6}{5}\right).25x=120\)
\(\left(-\frac{9}{8}\right).\left(-\frac{6}{5}\right).25x=120\)
\(\frac{27}{20}.25x=120\)\(25x=120:\frac{27}{20}=\frac{800}{9}\)
\(x=\frac{800}{9}:25=\frac{32}{9}\)
đợi tí đi nấu cơm đã
a) \(\left(-0,6\right)^6\cdot x=\left(\frac{-3}{5}\right)^8\)
\(x=\left(\frac{-3}{5}\right)^8:\left(\frac{-3}{5}\right)^6\)
\(x=\left(-\frac{3}{5}\right)^2=\frac{9}{25}\)
b) \(\left(0,5-x\right)^3=-8=\left(-2\right)^3\)
\(\Leftrightarrow0,5-x=-2\)
\(\Leftrightarrow x=2,5\)
Vậy,.................