Toán Lớp 8: B=x+8/x+5
1, Tìm số tự nhiên x để b ∈ z
2, Tìm x ∈ z để b là số nguyên dương
Leave a reply
Register Now
Login
Lost Password
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Toán Lớp 8: B=x+8/x+5
1, Tìm số tự nhiên x để b ∈ z
2, Tìm x ∈ z để b là số nguyên dương
Comments ( 2 )
x = – 2\\
x = – 4
\end{array} \right.\)
1)B = \dfrac{{x + 8}}{{x + 5}} = \dfrac{{x + 5 + 3}}{{x + 5}} = 1 + \dfrac{3}{{x + 5}}\\
B \in Z \to \dfrac{3}{{x + 5}} \in Z\\
\to x + 5 \in U\left( 3 \right)\\
\to \left[ \begin{array}{l}
x + 5 = 3\\
x + 5 = – 3\\
x + 5 = 1\\
x + 5 = – 1
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = – 2\\
x = – 8\\
x = – 4\\
x = – 6
\end{array} \right.\\
Do:x \in N\\
\to x \in \emptyset \\
b)Xét:\left[ \begin{array}{l}
x + 5 = 3\\
x + 5 = – 3\\
x + 5 = 1\\
x + 5 = – 1
\end{array} \right. \to \left[ \begin{array}{l}
B = 1 + \dfrac{3}{3} = 2\\
B = 1 + \dfrac{3}{{ – 3}} = 0\\
B = 1 + \dfrac{3}{1} = 4\\
B = 1 + \dfrac{3}{{ – 1}} = – 2
\end{array} \right.\\
Do:B \in N*\\
\to \left[ \begin{array}{l}
x = – 2\\
x = – 4
\end{array} \right.
\end{array}\)