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Ta có: \(\frac{4^6.25^5-2^{12}.25^4}{2^{12}.5^8-10^8.64}=\frac{2^{12}.5^{10}-2^{12}.5^8}{2^{12}.5^8-2^8.5^8.2^6}\)
\(=\frac{2^{12}.\left(5^{10}-5^8\right)}{2^{12}.5^8-2^{14}.5^8}\)
\(=\frac{2^{12}.5^8.\left(5^2-1\right)}{5^8.\left(2^{12}-2^{14}\right)}\)
\(=\frac{2^{12}.5^8.24}{5^8.2^{12}.\left(1-2^2\right)}\)
\(=\frac{24}{-3}\)
\(=-8\)
Học "tuốt" nha^^
\(a)A=\dfrac{2^{12}.3^5-4^6.9^2}{\left(2^2.3\right)^6+8^4.3^5}-\dfrac{5^{10}.7^3-25^5.49^2}{\left(125.7\right)^3+5^9.14^3}\)
\(A=\dfrac{2^{12}.3^5-\left(2^2\right)^63.\left(3^2\right)^2}{\left(2^2\right)^6.3^6+\left(2^3\right)^4.3^5}-\dfrac{5^{10}.7^3-\left(5^2\right)^5.\left(7^2\right)^2}{\left(5^3\right)^3.7^3+5^9.\left(7.2\right)^3}\)
\(A=\dfrac{2^{12}.3^5-2^{12}.3^5}{2^{12}.3^6+2^{12}.3^5}-\dfrac{5^{10}.7^3-5^{10}.7^4}{5^6.7^3+5^9.7^3.2^3}\)
\(A=\dfrac{0}{2^{12}.3^6+2^{12}.3^5}-\dfrac{5^{10}.7^3\left(1-7\right)}{5^6.7^3\left(1+5^3+2^3\right)}\)
\(A=0-\dfrac{5^4.\left(-6\right)}{1+125+8}\)
\(A=0-\dfrac{625.\left(-6\right)}{134}\)
\(A=\dfrac{-3750}{134}\)\(=\dfrac{-1875}{67}\)
\(b)3^{n+2}-2^{n+2}+3^n-2^n\)
\(=3^n.3^2-2^n.2^2+3^n-2^n\)
\(=(3^n.9+3^n)-\left(2^n.4+2^n\right)\)
\(=3^n.10-2^n.5\)
\(=3^n.10-2^{n-1}.10\)
\(=10\left(3^n-2^{n-1}\right)⋮10\)
\(Suy\) \(ra:\) \(3^{n+2}-2^{n+2}+3^n-2^n⋮10\)
b. Ta có: \(3^{n +2}-2^{n+2}+3^n-2^n\)
\(=\left(3^{n+2}+3^n\right)-\left(2^{n+2}+2^n\right)\)
\(=\left(3^n.3^2+3^n\right)-\left(2^{n-1}.2^3+2^{n-1}.2\right)\)
\(=3^n.\left(3^2+1\right)-2^{n-1}\left(2^3+2\right)\)
\(=3^n.10-2^{n-1}.10⋮10\)
\(\dfrac{-6}{25}+\left|\dfrac{-4}{5}\right|-\left|\dfrac{2}{25}\right|\)
\(=\dfrac{-6}{25}+\dfrac{4}{5}-\dfrac{2}{25}\)
\(=\dfrac{-6}{25}+\dfrac{20}{25}-\dfrac{2}{25}\)
\(=\dfrac{12}{25}\)
b) \(\dfrac{5}{9}-\left|\dfrac{4}{9}\right|+\left|\dfrac{8}{5}\right|\)
\(=\dfrac{5}{9}-\dfrac{4}{9}+\dfrac{8}{5}\)
\(=\dfrac{1}{9}+\dfrac{8}{5}\)
\(=\dfrac{5}{45}+\dfrac{72}{45}\)
\(=\dfrac{77}{45}\)