a) lim fx= -2.Tính lim (3fx-2x^2) x->2 x->2 b) lim (3x^2-x+10)/(ax^2-x-11)=2/3. Tính a-a^2 x-> – vô cực

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1. $a) \displaystyle\lim_{x \to 2} (3f(x)-2x^2)\\ =\displaystyle\lim_{x \to 2} 3f(x)-\displaystyle\lim_{x \to 2} 2x^2\\ =3\displaystyle\lim_{x \to 2} f(x)-2\displaystyle\lim_{x \to 2} x^2\\ =3.(-2)-2.2^2\\ =-14\\ b)\displaystyle\lim_{x \to -\infty} \dfrac{3x^2-x+10}{ax^2-x-11}\\  =\displaystyle\lim_{x \to -\infty} \dfrac{3-\dfrac{1}{x}+\dfrac{10}{x}}{a-\dfrac{1}{x}-\dfrac{11}{x}}\\ =\displaystyle\lim_{x \to -\infty} \dfrac{3-\dfrac{1}{x}+\dfrac{10}{x}}{a-\dfrac{1}{x}-\dfrac{11}{x}}\\ =\dfrac{3}{a}\\ =\dfrac{2}{3}\\ \Rightarrow a=\dfrac{9}{2}\\ \Rightarrow a-a^2=\dfrac{-63}{4}$

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