Đề: Tìm x, y ∈ N biết a/ (x – 2) (5 -x) = 0 b/ (x – 1) (x^2 + 1) = 0 c/ (x -3) (2y + 1) = 7 d/ (2x + 1) (3y – 2) = 55

0 bình luận về “Đề: Tìm x, y ∈ N biết a/ (x – 2) (5 -x) = 0 b/ (x – 1) (x^2 + 1) = 0 c/ (x -3) (2y + 1) = 7 d/ (2x + 1) (3y – 2) = 55”

1. \(\begin{array}{l}
   a)\,TH1:x – 2 = 0\,hay\,x = 0 + 2 = 2\\
   TH2:\,5 – x = 0\,hay\,x = 5 – 0 = 5\\
   b)\,TH1:\,x – 1 = 0\,\,hay\,\,x = 0 + 1 = 1\\
   TH2:\,{x^2} + 1 = 0\,\,\left( {ktm\,do\,x \in N \Rightarrow {x^2} \ge 1 \Rightarrow {x^2} + 1 \ge 2 > 0} \right)\\
   c)\,TH1:\,\left\{ \begin{array}{l}
   x – 3 = 1\\
   2y + 1 = 7
   \end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}
   x = 4\\
   y = 3
   \end{array} \right.\left( {tm} \right)\\
   TH2:\,\left\{ \begin{array}{l}
   x – 3 = 7\\
   2y + 1 = 1
   \end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}
   x = 10\\
   y = 0
   \end{array} \right.\left( {tm} \right)\\
   d)\,TH1:\,\left\{ \begin{array}{l}
   2x + 1 = 1\\
   3y – 2 = 55
   \end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}
   x = 0\\
   y = 19
   \end{array} \right.\left( {tm} \right)\\
   TH2:\,\left\{ \begin{array}{l}
   2x + 1 = 55\\
   3y – 2 = 1
   \end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}
   x = 27\\
   y = 1
   \end{array} \right.\left( {tm} \right)\\
   TH3:\,\left\{ \begin{array}{l}
   2x + 1 = 5\\
   3y – 2 = 11
   \end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}
   x = 2\\
   y = \dfrac{{13}}{3}
   \end{array} \right.\left( {ktm} \right)\\
   TH4:\,\left\{ \begin{array}{l}
   2x + 1 = 11\\
   3y – 2 = 5
   \end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}
   x = 5\\
   y = \dfrac{7}{3}
   \end{array} \right.\left( {ktm} \right)
   \end{array}\)

    

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