## 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

Question

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

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4 tuần 2021-09-07T08:10:21+00:00 1 Answers 5 views 0

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