1)
a) Có: \(A=x^2-\dfrac{1}{9}=0\)
\(\Rightarrow x^2=\dfrac{1}{9}\Rightarrow x=\pm\dfrac{1}{3}\)
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b) Có: \(B=x^2+2x+1=0\)
\(\Rightarrow B=x^2+x+x+1\)
\(\Rightarrow B=x\left(x+1\right)+1\left(x+1\right)\)
\(\Rightarrow B=\left(x+1\right)^2=0\)
\(\Rightarrow x=-1\)
2) Thay x=-1 vào Q(x), có:
\(Q\left(x\right)=5.\left(-1\right)^2-5+a^2-a\)
\(\Rightarrow Q\left(x\right)=5.1-5+a^2-a\)
\(\Rightarrow Q\left(x\right)=a^2-a\)
\(\Rightarrow Q\left(x\right)=a\left(a-1\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}a=0\\a=1\end{matrix}\right.\)
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