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\(c,1.2.3...9-1.2.3...8-1.2.3...7.8^2\)
\(=1.2.3...8\left(9-1-8\right)\)
\(=1.2.3...8.0\)
\(=0\)
\(d,\frac{\left(3.4.2^{16}\right)^2}{11.2^{13}.4^{11}-16^9}\)
\(=\frac{3^2.4^2.2^{32}}{11.2^{13}.\left(2^2\right)^{11}-\left(2^4\right)^9}\)
\(=\frac{3^2.2^4.2^{32}}{11.2^{13}.2^{22}-2^{36}}\)
\(=\frac{3^2.2^{36}}{11.2^{35}-2^{36}}\)
\(=\frac{3^2.2^{36}}{2^{35}\left(11-2\right)}\)
\(=\frac{3^2.2^{36}}{2^{35}.9}\)
\(=\frac{3^2.2^{36}}{2^{35}.3^2}\)
\(=2\)
12000-(3000+5400+1200)
=12000-9600
=24000
đúng cho mình nha bạn
12000-(1500.2+1800.3+1800.2/3)
=12000-9600
=24000
chọn nha mình nha các bạn! ^^
1200-(1500x2+1800x3+1800x2:3)
=1200-(3000+5400+3600:3)
=1200-(3000+5400+1200)
=1200-(8400+1200)
=1200-9600=-8400
12000 - (1500 x 2 + 1800 x 3 + 1800 x 2 : 3)
=12000-(3000+5400+1200)
=12000-9600
=2400
l-i-k-e nha!
\(\frac{2}{n\left(n+1\right)\left(n+2\right)}=\frac{n+2-n}{n\left(n+1\right)\left(n+2\right)}=\frac{n+2}{n\left(n+1\right)\left(n+2\right)}-\frac{n}{n\left(n+1\right)\left(n+2\right)}=\frac{1}{n\left(n+1\right)}-\frac{1}{n\left(n+2\right)}\)
\(\Rightarrow\frac{2}{1.2.3}+\frac{2}{2.3.4}+...+\frac{2}{98.99.100}=\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-\frac{1}{3.4}+...+\frac{1}{98.99}-\frac{1}{99.100}\)
\(=\frac{1}{1.2}-\frac{1}{99.100}\)
\(\Rightarrow\frac{1}{1.2.3}+...+\frac{1}{98.99.100}=\frac{1}{2}\left(\frac{1}{1.2}-\frac{1}{99.100}\right)\)
\(\Rightarrow k=2\)
\(12000-\left(1500.2+1800.3+1800.2:3\right)\)
= \(12000-\left(3000+5400+1200\right)\)
\(=12000-9600\)
\(=2400\)
\(\text{12000-(1500.2+1800.3+1800.2:3)}\)
\(\text{=12000-(3000+540+1200)}\)
\(\text{=12000-96000}\)
\(\text{=2400}\)