Rút gọn các biểu thức sau :
a) 10 x \(\frac{4^6.9^5+6^9.120}{8^4.3^{12}-6^{11}}\);
b) 1 + 2 + \(2^2\)+ \(2^3\)+\(2^4\)...... + \(2^{49}\)+ \(2^{50}\)
c) 5 + 5\(^3\)+ 5\(^5\)+......+ 5\(^{47}\)+ 5\(^{49}\).
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\(\dfrac{4^6.9^5+6^9.120}{8^4.3^{12}-6^{11}}\)
\(=\dfrac{2^{12}.3^{10}+2^9.3^9.2^3.3.5}{2^{12}.3^{12}-2^{11}.3^{11}}\)
\(=\dfrac{2^{12}.3^{10}+2^{12}.3^{10}.5}{2^{11}.3^{11}\left(2.3-1\right)}\)
\(=\dfrac{2^{12}.3^{10}\left(1+5\right)}{2^{11}.3^{11}.5}\)
\(=\dfrac{2^{12}.3^{10}.6}{2^{11}.3^{11}.5}=\dfrac{2.6}{3.5}=\dfrac{4}{5}\)
\(N=\frac{4^6.9^5+6^9.120}{8^4.3^{12}-6^{11}}=\frac{2^{12}.3^{15}+2^9.3^9.2^3.3.5}{2^{12}.3^{12}-2^{11}.3^{11}}=\frac{2^{12}.3^{15}+2^{12}.3^{10}.5}{2^{12}.3^{12}-2^{11}.3^{11}}=\frac{2^{12}.3^{10}\left(3^5+5\right)}{2^{11}.3^{11}\left(2.3-1\right)}\)
cho mk sửa lại xíu:
\(\frac{2^{12}.3^{10}\left(1+5\right)}{2^{11}.3^{11}.5}=\frac{2.6}{3.5}=\frac{12}{15}=\frac{4}{5}\)
mk sai xíu. hihi, học tốt nhé !
\(\frac{2^{12}.3^{10}+2^9.3^9.2^3.3.5}{2^{12}.3^{12}-2^{11}.3^{11}}=\frac{2^{12}.3^{10}+2^{12}.3^{10}.5}{2^{12}.3^{12}-2^{11}.3^{11}}=\frac{2^{12}.3^{10}.\left(1+5\right)}{2^{11}.3^{11}.\left(6-1\right)}=\frac{2.6}{3.5}=\frac{4}{5}\)
\(\frac{\left(2^2\right)^6.\left(3^2\right)^5+2^9.3^9.120}{\left(2^3\right)^4.3^{12}-2^{11}.3^{11}}\)=\(\frac{2^{12}.3^{10}+2^9.3^9.120}{2^{12}.3^{12}-2^{11}.3^{11}}\)=\(\frac{120}{3^2-2^3.3^3}\)=\(\frac{120}{9-8.27}\)=\(\frac{120}{-207}\)=\(\frac{-40}{69}\)
tk cho mk nhe