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A và B cùng dấu nên AB>0
=>\(2x^3\cdot\left(-3\right)x^4>0\)
=>\(x^7< 0\)
=>x<0

Xét ΔABC có \(\widehat{ABC}+\widehat{ACB}+\widehat{BAC}=180^0\)
=>\(2\cdot\left(\widehat{IBC}+\widehat{ICB}\right)=180^0-\widehat{BAC}\)
=>\(\widehat{IBC}+\widehat{ICB}=90^0-\dfrac{1}{2}\cdot\widehat{BAC}\)
Xét ΔBIC có \(\widehat{BIC}+\widehat{IBC}+\widehat{ICB}=180^0\)
=>\(\widehat{BIC}+90^0-\dfrac{1}{2}\widehat{BAC}=180^0\)
=>\(\widehat{BIC}=180^0-90^0+\dfrac{1}{2}\cdot\widehat{BAC}=90^0+\dfrac{1}{2}\cdot\widehat{BAC}\)

\(\left(3x-2\right)^{2004}=\left(3x-2\right)^{2006}\)
=>\(\left(3x-2\right)^{2006}-\left(3x-2\right)^{2004}=0\)
=>\(\left(3x-2\right)^{2004}\left[\left(3x-2\right)^2-1\right]=0\)
=>\(\left(3x-2\right)^{2004}\cdot\left(3x-3\right)\left(3x-1\right)=0\)
=>\(\left[{}\begin{matrix}3x-2=0\\3x-3=0\\3x-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{3}\\x=1\\x=\dfrac{1}{3}\end{matrix}\right.\)
\(\left(3x-2\right)^{2004}=\left(3x-2\right)^{2006}\\ =>\left(3x-2\right)^{2006}-\left(3x-2\right)^{2004}=0\\ =>\left(3x-2\right)^{2004}\left[\left(3x-2\right)^2-1\right]=0\)
+) \(\left(3x-2\right)^{2004}=0=>3x-2=0=>x=\dfrac{2}{3}\)
+) \(\left(3x-2\right)^2-1=0=>\left(3x-2\right)^2=1^2\)
\(TH1:3x-2=1=>3x=1+2=3=>x=\dfrac{3}{3}=1\\ TH2:3x-2=-1=>3x=-1+2=1=>x=\dfrac{1}{3}\)

`A(x) + B(x) = 6x^4 - 3x^2 - 5`
`A(x) - B(x) = 4x^4 - 6x^3 + 7x^2 + 8x - 9`
Áp dụng bài toán tổng hiệu ta có:
`A(x) = [(6x^4 - 3x^2 - 5) + (4x^4 - 6x^3 + 7x^2 + 8x - 9)] : 2`
`= (6x^4 - 3x^2 - 5 + 4x^4 - 6x^3 + 7x^2 + 8x - 9) : 2`
`= (10x^4 - 6x^3 + 4x^2 + 8x - 14) : 2`
`= 5x^4 - 3x^3 + 2x^2 + 4x - 7`
`B(x) = (6x^4 - 3x^2 - 5) - (5x^4 - 3x^3 + 2x^2 + 4x - 7)`
`= 6x^4 - 3x^2 - 5 - 5x^4 + 3x^3 - 2x^2 - 4x + 7`
`= x^4 + 3x^3 - 5x^2 - 4x + 2`
Vậy ....
\(2A\left(x\right)=\left(6x^4-3x^2-5\right)+\left(4x^4-6x^3+7x^2+8x-9\right)\\ =\left(6x^4+4x^4\right)-6x^3+\left(-3x^2+7x^2\right)+8x+\left(-5-9\right)\\ =10x^4-6x^3+4x^2+8x-14\\ =>A\left(x\right)=5x^4-3x^3+2x^2+4x-7\)
\(=>B\left(x\right)=\left(6x^4-3x^2-5\right)-A\left(x\right)\\ =\left(6x^4-3x^2-5\right)-\left(5x^4-3x^3+2x^2+4x-7\right)\\ =\left(6x^4-5x^4\right)+3x^3+\left(-3x^2-2x^2\right)-4x+\left(-5+7\right)\\ =x^4+3x^3-5x^2-4x+2\)


\(\dfrac{1}{3}\cdot x+\dfrac{2}{5}\cdot\left(x+1\right)=0\\ =>\dfrac{1}{3}\cdot x+\dfrac{2}{5}\cdot x+\dfrac{2}{5}=0\\ =>x\cdot\left(\dfrac{1}{3}+\dfrac{2}{5}\right)+\dfrac{2}{5}=0\\ =>x\cdot\dfrac{11}{15}+\dfrac{2}{5}=0\\ =>x\cdot\dfrac{11}{15}=-\dfrac{2}{5}\\ =>x=\dfrac{-2}{5}:\dfrac{11}{15}\\ =>x=\dfrac{-2}{5}\cdot\dfrac{15}{11}\\ =>x=\dfrac{-6}{11}\)
\(\dfrac{8^{11}\cdot3^{17}}{27^{10}\cdot9^{15}}=\dfrac{2^{33}\cdot3^{17}}{3^{30}\cdot3^{30}}=\dfrac{2^{33}\cdot3^{17}}{3^{60}}=\dfrac{2^{33}}{3^{43}}\)
\(\dfrac{8^{11}.3^{17}}{27^{10}.9^{15}}\\ =\dfrac{\left(2^3\right)^{11}.3^{17}}{\left(3^3\right)^{10}.\left(3^2\right)^{15}}\\ =\dfrac{2^{33}.3^{17}}{3^{30}.3^{30}}\\ =\dfrac{2^{33}.3^{17}}{3^{60}}\\ =\dfrac{2^{33}}{3^{43}}\)