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a, \(A+B=4x^5-7y^2+2xy-x-5y-14-6x^5-2y^2+3x-15y+6=-2x^5-9y^2+2xy+2x-20y-8\)
\(A-B=4x^5-7y^2+2xy-x-5y-14+6x^5+2y^2-3x+15y-6=10x^5-5y^2+2xy-4x+10y-20\)
b, A + B bậc 5 ; A - B bậc 5
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\(\left(x-1\right)\left(\dfrac{3}{4}x+\dfrac{1}{2}\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=1\\\dfrac{3}{4}x=-\dfrac{1}{2}\end{matrix}\right.\)\(\Rightarrow\left[{}\begin{matrix}x=1\\x=-\dfrac{2}{3}\end{matrix}\right.\)
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\(\dfrac{x}{y}=\dfrac{y}{z}=\dfrac{z}{t}=\dfrac{t}{x}=\dfrac{x+y+z+t}{y+z+t+x}=1\\ \Rightarrow\left\{{}\begin{matrix}x=y\\y=z\\z=t\\t=x\end{matrix}\right.\Rightarrow x=y=z=t\\ \Rightarrow M=\dfrac{2x-x}{x+x}+\dfrac{2x-x}{x+x}+\dfrac{2x-x}{x+x}+\dfrac{2x-x}{x+x}=\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}=2\)
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\(a,\left|a\right|=2\Leftrightarrow a=2\left(a>0\right)\Leftrightarrow y=f\left(x\right)=2x\\ f\left(-2\right)=\left(-2\right).2=-4\\ f\left(4\right)=2.4=8\\ b,f\left(2\right)=2a=6\Leftrightarrow a=3\)
\(\left[{}\begin{matrix}3x-2=0\\4-x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{3}\\x=4\end{matrix}\right.\)
3x-2=0
3x=2
X=2/3
hoặc 4-x=0
X=4-0
X=4