a, (a+1) chia hết cho (a-1) b, 5x+13 là bội của 2x+1 Giúp mk nha. Uk vote 5 ???? 09/07/2021 Bởi Arianna a, (a+1) chia hết cho (a-1) b, 5x+13 là bội của 2x+1 Giúp mk nha. Uk vote 5 ????
Đáp án: $\begin{array}{l}a)a + 1 = a – 1 + 2\\Do:\left( {a – 1} \right) \vdots \left( {a – 1} \right)\\ \Rightarrow 2 \vdots \left( {a – 1} \right)\\ \Rightarrow \left( {a – 1} \right) \in Ư\left( 2 \right) = \{ – 2; – 1;1;2\} \\ \Rightarrow a \in \{ – 1;0;2;3\} \\b)\left( {5x + 13} \right) \vdots \left( {2x + 1} \right)\\ \Rightarrow 2\left( {5x + 13} \right) \vdots \left( {2x + 1} \right)\\Do:2\left( {5x + 13} \right) = 10x + 26 = 10x + 5 + 21\\ = 5\left( {2x + 1} \right) + 21\\Do:5\left( {2x + 1} \right) \vdots \left( {2x + 1} \right)\\ \Rightarrow 21 \vdots \left( {2x + 1} \right)\\ \Rightarrow \left( {2x + 1} \right) \in Ư\left( {21} \right) = \{ – 21; – 7; – 3; – 1;1;3;7;21\} \\ \Rightarrow x \in \{ – 11; – 4; – 2; – 1;0;1;3;10\} \end{array}$ Bình luận
Đáp án:
$\begin{array}{l}
a)a + 1 = a – 1 + 2\\
Do:\left( {a – 1} \right) \vdots \left( {a – 1} \right)\\
\Rightarrow 2 \vdots \left( {a – 1} \right)\\
\Rightarrow \left( {a – 1} \right) \in Ư\left( 2 \right) = \{ – 2; – 1;1;2\} \\
\Rightarrow a \in \{ – 1;0;2;3\} \\
b)\left( {5x + 13} \right) \vdots \left( {2x + 1} \right)\\
\Rightarrow 2\left( {5x + 13} \right) \vdots \left( {2x + 1} \right)\\
Do:2\left( {5x + 13} \right) = 10x + 26 = 10x + 5 + 21\\
= 5\left( {2x + 1} \right) + 21\\
Do:5\left( {2x + 1} \right) \vdots \left( {2x + 1} \right)\\
\Rightarrow 21 \vdots \left( {2x + 1} \right)\\
\Rightarrow \left( {2x + 1} \right) \in Ư\left( {21} \right) = \{ – 21; – 7; – 3; – 1;1;3;7;21\} \\
\Rightarrow x \in \{ – 11; – 4; – 2; – 1;0;1;3;10\}
\end{array}$
Mk trình bày chi tiết trong hình!
Vote mk 5 *n