Câu 9 : 

n_SO2 = 1.12/22.4 = 0.05 (mol) 

Zn + 2H₂SO_4(đn) => ZnSO₄ + SO₂ + 2H₂O

0.05...............................................0.05

Al thụ động với H₂SO₄ đặc nguội 

m_Zn = 0.05 * 65 = 3.25 (g) 

m_Al = 8 - 3.25 = 4.75 (g) 

Câu 9 : 

n_SO2 = 2.24/22.4 = 0.1 (mol) 

Mg + 2H₂SO_4(đn) => MgSO₄ + SO₂ + 2H₂O

0.1................................................0.1

Fe thụ động với H₂SO₄ đặc nguội 

m_Mg = 0.1 * 24 = 2.4 (g) 

m_Fe = 8 - 2.4 = 5.6 (g) 

\(\lim\limits_{ }\dfrac{-3n+2}{n^3+2n-1}\)

\(=\lim\limits_{ }\dfrac{n\left(-3+\dfrac{2}{n}\right)}{n^3\left(1+\dfrac{2}{n^2}-\dfrac{1}{n^3}\right)}\)

\(=\lim\limits_{ }\dfrac{-3}{n^2}\)

\(=0\)

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\(P\left(1\right)=a+b+c=0\)

\(P\left(-1\right)=a\cdot\left(-1\right)^2+b\left(-1\right)+c=6\)

\(\Leftrightarrow P\left(-1\right)=a-b+c=6\)

\(P\left(-2\right)=a\cdot\left(-2\right)^2+b\left(-2\right)+c=3\)

\(\Leftrightarrow P\left(-2\right)=4a-2b+c=3\)

\(\text{Khi đó : }\)

\(a=-2\)

\(b=-3\)

\(c=5\)

\(P\left(x\right)=-2x^2-3x+5\)

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