Toán Lớp 6: Tìm x : ( 2x + 3 ) chia hết cho ( x – 1)
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Toán Lớp 6: Tìm x : ( 2x + 3 ) chia hết cho ( x – 1)
Comments ( 2 )
Tham khảo:
( 2x + 3 ) \vdots ( x – 1 )
2x – 2 + 5 \vdots x – 1
2(x – 1 ) + 5 \vdots x – 1
<=> 2( x – 1 ) \vdots x – 1
=> 5 \vdots x – 1
=> x – 1 \in Ư(5) = { -5; -1; 1; 5 }
=> x \in { -4; 0; 2; 6 }
( 2x + 3 ) chia hết cho ( x -1 )
-> 2x – 2 + 5 chia hết cho x – 1
-> 2. ( x – 1 ) + 5 chia hết cho x – 1
Mà 2.( x – 1) chia hết cho x -1
-> 5 chia hết cho x -1
-> x-1∈ Ư( 5 ) ={-5,-1, 1,5}
-> x∈ {-4, 0, 2, 6}
Mà x bé nhất
Nên x = -4