Toán Lớp 6: Tìm x€Z biết:
a)x+6 chia hết cho x
b)x+9 chia hết cho x+1
c)2x +1 chia hết cho x-1
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Toán Lớp 6: Tìm x€Z biết:
a)x+6 chia hết cho x
b)x+9 chia hết cho x+1
c)2x +1 chia hết cho x-1
Comments ( 1 )
a) x + 6 ⋮x + 1
=> ( x + 1 ) + 5 ⋮x + 1
=> 5 ⋮x + 1
=> x + 1 ∈Ư( 5) = { -5; -1; 1; 5 }
=> x ∈{ -6; -2; 0; 4 }
Vậy x ∈{ -6; -2; 0; 4 }
b) ( x +9) – (x + 1) ⋮(x + l)
=>8 ⋮ (x + l)
=> x + 1 \in Ư(8) = { – 8; -4; -2; -1; 1; 2; 4; 8}
Vậy x \in {- 9; – 5; – 3; – 2; 0; 1; 3; 7}
c) (2 + 1) -2 (x – 1) ⋮ (x – 1)
=> 3 ⋮ (x – 1)
=> x – 1 \in Ư (3) = {- 3; -1; 1; 3}
Vậy x \in{ – 2; 0; 2; 4}