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\(P=\dfrac{16^7\cdot5^3\left(5-1\right)}{16^7\cdot\left(25^2-5^3\right)}=\dfrac{5^3\cdot2^2}{5^4-5^3}=\dfrac{5^3\cdot2^2}{5^3\cdot\left(5-1\right)}=1\)
\(\frac{16^7\times5^4-8^8\times16\times5^2\times125}{16^7\times25^2-8^7\times128\times5^5}\)
\(=\frac{16^7\times5^4-8^8\times2^4\times5^2\times5^3}{16^7\times5^4-8^7\times2^7\times5^5}\)
\(=\frac{8}{2^3}\)
\(=\frac{8}{8}\)
\(=1\)
\(9^7+81^4-27^5\)
\(=\left(3^2\right)^7+\left(3^4\right)^4-\left(3^3\right)^5\)
\(=3^{14}+3^{16}-3^{15}\)
\(=3^{14}.\left(1+3^2-3\right)\)
\(=3^{14}.7⋮7\)
=> đpcm
\(25^{25}+5^{49}-125^{16}\)
\(=\left(5^2\right)^{25}+5^{49}-\left(5^3\right)^{16}\)
\(=5^{50}+5^{49}-5^{48}\)
\(=5^{48}.\left(5^2+5-1\right)\)
\(=5^{48}.29⋮29\)
=> đpcm
Bài làm :
\(\text{1) }9^7+81^4-27^5\)
\(=\left(3^2\right)^7+\left(3^4\right)^4-\left(3^3\right)^5\)
\(=3^{14}+3^{16}-3^{15}\)
\(=3^{14}\left(1+3^2-3\right)\)
\(=3^{14}.7⋮7\)
=> Điều phải chứng minh
\(\text{2)}25^{25}+5^{49}-125^{16}\)
\(=\left(5^2\right)^{25}+5^{49}-\left(5^3\right)^{16}\)
\(=5^{50}+5^{49}-5^{48}\)
\(=5^{48}\left(5^2+5-1\right)\)
\(=5^{48}.29⋮29\)
=> Điều phải chứng minh
a) \(9^7+81^4-27^5=\left(3^2\right)^7+\left(3^4\right)^4-\left(3^3\right)^5\)
\(=3^{14}+3^{16}-3^{15}\)
\(=3^{14}\left(1+3^2-3\right)=3^{14}\cdot7⋮7\left(đpcm\right)\)
b) \(25^{25}+5^{49}-125^{16}=\left(5^2\right)^{25}+5^{49}-\left(5^3\right)^{16}\)
\(=5^{50}+5^{49}-5^{48}=5^{48}\left(5^2+5-1\right)\)
\(=5^{48}\cdot29⋮29\left(đpcm\right)\)
\(125^7:25^{16}\\ =\left(5^3\right)^7:\left(5^2\right)^{16}\\ =5^{3\cdot7}:5^{2\cdot16}\\ =5^{21}:5^{32}\\ =5^{21-32}\\ =5^{-11}\)