Các số tự nhiên \(x\) sao cho:
\(a,\ 8~\vdots \left( x-1 \right)\)
\(b,\ 70~\vdots \left( 2x-3 \right)\)
\(c,\ x+2~\in \)\(U\left( 16 \right)\)
\(d,\ 2x+1~\in \)\(U\left( 21 \right)\)
Câu 213209: Các số tự nhiên \(x\) sao cho:
\(a,\ 8~\vdots \left( x-1 \right)\)
\(b,\ 70~\vdots \left( 2x-3 \right)\)
\(c,\ x+2~\in \)\(U\left( 16 \right)\)
\(d,\ 2x+1~\in \)\(U\left( 21 \right)\)
A. \(a,\ x \in \left\{ {2;3;5;9} \right\}\)
\(b,\ x \in \left\{ {4;5;19} \right\}\)
\(c,\ x \in \left\{ {0;2;6;14} \right\}\)
\(d,\ x \in \left\{ {1;3;10} \right\}\)
B. \(a,\ x \in \left\{ {2;3;5} \right\}\)
\(b,\ x \in \left\{ {2;4;5;19} \right\}\)
\(c,\ x \in \left\{ {0;2;6} \right\}\)
\(d,\ x \in \left\{ {0;1;3;10} \right\}\)
C. \(a,\ x \in \left\{ {2;3;5;9} \right\}\)
\(b,\ x \in \left\{ {2;4;5;19} \right\}\)
\(c,\ x \in \left\{ {0;2;6;14} \right\}\)
\(d,\ x \in \left\{ {0;1;3;10} \right\}\)
D. \(a,\ x \in \left\{ {2;3;5;9} \right\}\)
\(b,\ x \in \left\{ {2;4;19} \right\}\)
\(c,\ x \in \left\{ {0;2;6;14} \right\}\)
\(d,\ x \in \left\{ {0;1;3} \right\}\)
\(U\left( a \right)=\left\{ x\in N|a\vdots x \right\}\).
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Đáp án : C(1) bình luận (0) lời giải
Giải chi tiết:
\(\begin{array}{l}a)\,8 \vdots \left( {x - 1} \right) \Rightarrow \left( {x - 1} \right) \in U\left( 8 \right)\\ \Rightarrow \left( {x - 1} \right) \in \left\{ {1;2;4;8} \right\}\\ \Rightarrow x \in \left\{ {2;3;5;9} \right\}\end{array}\)
\(\begin{array}{l}b)70 \vdots \left( {2x - 3} \right)\\70 \vdots \left( {2x - 3} \right) \Rightarrow \left( {2x - 3} \right) \in U\left( {70} \right)\\ \Rightarrow 2x - 3 \in \left\{ {1;2;5;7;10;14;35;70} \right\}\\ \Rightarrow 2x \in \left\{ {4;5;8;10;13;17;38;73} \right\}\\ \Rightarrow x \in \left\{ {2;4;5;19} \right\}\end{array}\)
\(\begin{array}{l}c)x + 2 \in U\left( {16} \right)\\ \Rightarrow x + 2 \in \left\{ {1;2;4;8;16} \right\}\\ \Rightarrow x \in \left\{ {0;2;6;14} \right\}\end{array}\)
\(\begin{array}{l}d)2x + 1 \in U\left( {21} \right)\\ \Rightarrow 2x + 1 \in \left\{ {1;3;7;21} \right\}\\ \Rightarrow 2x \in \left\{ {0;2;6;20} \right\}\\ \Rightarrow x \in \left\{ {0;1;3;10} \right\}\end{array}\)
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