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Ta có:\(x=18\Rightarrow\hept{\begin{cases}x+1=19\\-x-1=-19\end{cases}}\)
Thay vào BT D ta được:
\(D=x^{12}+\left(-x-1\right)x^{11}+\left(x+1\right)x^{10}+\left(-x-1\right)x^9+...+\left(x+1\right)x^2+\left(-x-1\right)x+1\)
\(=x^{12}-x^{12}-x^{11}+x^{11}+x^{10}-x^{10}-x^9+...+x^3+x^2-x^2-x+1\)
\(=1-x\)
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https://olm.vn/hoi-dap/tim-kiem?q=%7C2x-9%7C+%7C3x-13%7C-%7C14-5x%7C+%7C19-(4x+12)%7C=56t%C3%ACm+x&id=191953
\(\Leftrightarrow\left[{}\begin{matrix}14-19x=7x-15\\19x-14=7x-15\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}26x=29\\12x=-1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{29}{26}\\x=-\dfrac{1}{12}\end{matrix}\right.\)
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{ x2 - [ 62 - ( 82 - 9.7)3 - 7.5]3 - 5.3 }3 = 1
{ x2 + [ 36 - (64 - 63)3 - 35]3 - 15}3 = 1
[ x2 - ( 36 - 13 - 35 ) - 15 ]3 = 1
[ x2 - ( 36 - 1 - 35 ) - 15]3 = 1
[ x2 - ( 35 - 35 ) - 15]3 = 1
[ x2 - 0 - 15]3 = 1
( x2 - 15 )3 = 1
<=> ( x2 - 15)3 = 13
=> x2 - 15 = 1
<=> x2 = 16
=> x = 4
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\(a,\frac{20^{12}\cdot6^{14}}{8^{13}\cdot15^{12}}\)
\(=\frac{5^{12}\cdot2^{24}\cdot2^{14}\cdot3^{14}}{2^{39}\cdot3^{12}\cdot5^{12}}\)
\(=\frac{5^{12}\cdot2^{38}\cdot3^{14}}{2^{39}\cdot3^{12}\cdot5^{12}}=\frac{3^2}{2}=\frac{9}{2}\)
\(b,\frac{45^{12}\cdot10^{14}}{18^{13}\cdot25^{12}}\)
\(=\frac{5^{12}\cdot3^{24}\cdot2^{14}\cdot5^{14}}{2^{13}\cdot3^{26}\cdot5^{24}}\)
\(=\frac{5^{26}\cdot3^{24}\cdot2^{14}}{2^{13}\cdot3^{26}\cdot5^{24}}=\frac{5^2\cdot2}{3^2}=\frac{50}{9}\)
\(c,\frac{18^{12}\cdot27^8}{6^8\cdot3^{40}}\)
\(=\frac{2^{12}\cdot3^{24}\cdot3^{24}}{2^8\cdot3^8\cdot3^{40}}\)
\(=\frac{2^{12}\cdot3^{48}}{2^8\cdot3^{48}}=2^4=16\)
\(d,\frac{12^{14}\cdot9^{18}}{8^9\cdot27^{17}}\)
\(=\frac{3^{14}\cdot2^{28}\cdot3^{36}}{2^{27}\cdot3^{51}}\)
\(=\frac{3^{50}\cdot2^{28}}{2^{27}\cdot3^{51}}=\frac{2}{3}\)
làm hơi tắt nên chịu khó hiểu
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3/17 - 5/13 - 18/35 + 14/17 + 17/-35 - 8/13
=(3/17+14/17)+(-5/13-8/13)+(-18/35+17/35)
=1+(-1)+(-1/35)
=-1/35
Chúc bn học tốt
\(\frac{3}{17}-\frac{5}{13}-\frac{18}{35}+\frac{14}{17}\)\(+\frac{17}{-35}-\frac{8}{13}\)
\(=\left(\frac{3}{17}+\frac{14}{17}\right)\)\(-\left(\frac{18}{35}-\frac{-17}{35}\right)\)\(-\left(\frac{5}{13}+\frac{8}{13}\right)\)
\(=1-1-1\)\(=0\)