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\(\dfrac{81}{125}=\dfrac{3^4}{5^3}\)
\(\dfrac{-8}{27}=\dfrac{\left(-2\right)^3}{3^3}=\left(\dfrac{-2}{3}\right)^3\)
Ta có:
\(\dfrac{81}{125}=\dfrac{3^4}{5^4}=\left(\dfrac{3}{5}\right)^4\)
\(-\dfrac{8}{27}=-\dfrac{2^3}{3^3}=\left(-\dfrac{2}{3}\right)^3\)
\(\dfrac{81}{125}-\dfrac{8}{27}=\dfrac{3^4}{5^3}-\dfrac{2^3}{3^3}\)
-8/27 = (-2/3)3 nha còn cái kia mình cụng ko bít đâu mình cũng đang hỏi
1.
a) x : \(\left(\dfrac{3}{4}\right)^3\) =\(\left(\dfrac{3}{4}\right)^3\)
x = \(\left(\dfrac{3}{4}\right)^3.\left(\dfrac{3}{4}\right)^3\)
x = \(\dfrac{3}{4}^{3+3}\)
x = \(\dfrac{3}{4}^6\)
x = \(\dfrac{729}{4096}\)
b) \(\left(\dfrac{2}{5}\right)^5.x=\left(\dfrac{2}{5}\right)^8\)
x = \(\left(\dfrac{2}{5}\right)^8:\left(\dfrac{2}{5}\right)^5\)
x = \(\dfrac{2}{5}^{8-5}\)
x = \(\dfrac{2}{5}^3\)
x = \(\dfrac{8}{5}\)
2.
(0,36)\(^8\) \([\left(0,6\right)^3]^8\) = (0,6)\(^{3.8}\) = ( 0,6)\(^{24}\)
( 0,216)\(^4\) = \([\left(0,6\right)^3]^4\) = (0.6)\(^{3.4}\) = ( 0,6)\(^{12}\)
\(x:\left(\dfrac{3}{4}\right)^3=\left(\dfrac{3}{4}\right)^2\)
\(x=\left(\dfrac{3}{4}\right)^2.\left(\dfrac{3}{4}\right)^3\) <=> \(x=\left(\dfrac{3}{4}\right)^{2+3}\)
=> \(x=\left(\dfrac{3}{4}\right)^5\)
b, \(\left(\dfrac{2}{5}\right)^5.x=\left(\dfrac{2}{5}\right)^8\)
\(x=\left(\dfrac{2}{5}\right)^8:\left(\dfrac{2}{5}\right)^5\Leftrightarrow x=\left(\dfrac{2}{5}\right)^{8-5}\)
=>\(x=\left(\dfrac{2}{5}\right)^3\)
bài 2 : Với bài này ta cần áp dụng quy tắc: \(\left(x^m\right)^n=x^{m.n}\)
\(0,36^8=\left[\left(0,6\right)^2\right]^8=\left(0,6\right)^{16}\)
\(0,216^4=\left[\left(0,6\right)^3\right]^4=\left(0,6\right)^{12}\)
\(\frac{81}{125}\) viết dưới dạng luỹ thừa là : \(\frac{3^4}{5^3}\)
\(-\frac{8}{27}\) viết dưới dạng luỹ thừa là : \(-\frac{2^3}{3^3}\)
\(\dfrac{81}{125}=\dfrac{3^4}{5^3}\) ; \(-\dfrac{8}{27}=-\left(\dfrac{2}{3}\right)^3\)