Toán Lớp 6: tìm số nguyên x biết:
a)7:(x-1)
b)(x-3).(x-5)
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Toán Lớp 6: tìm số nguyên x biết:
a)7:(x-1)
b)(x-3).(x-5)
Comments ( 2 )
Lời giải và giải thích chi tiết:
$\textit{a) 7 $\vdots$ (x – 1)}$
$\textit{→ Ư(7) = {-7;-1;1;7}}$
$\textit{→ $x$ ∈ {-6;0;2;8}}$
$\textit{b) (x – 3) $\vdots$ (x – 5)}$
$\textit{→ ($x$ – 5 + 2) $\vdots$ ($x$ – 5}$
$\textit{→ 2 $\vdots$ (x – 5)}$
$\textit{→ Ư(2) = {-2;-1;1;2}}$
$\textit{$x$ ∈ {3;4;6;7}}$
$\textit{N hắc ám}$
a) 7 vdots (x-1)
=> (x-1) in Ư(7)={-7; -1; 1; 7}
=> x in {-6; 0; 2; 8}
b) (x-3) vdots (x-5)
=> (x-5+2) vdots (x-5)
=> 2 vdots (x-5)
=> (x-5) in Ư(2)={-2; -1; 1; 2}
=> x in {3; 4; 6; 7}