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