Toán tìm x để B là số nguyên : B= $\frac{3x-2}{x+1}$ làm hộ mk vớiiiii 10/10/2021 By Josephine tìm x để B là số nguyên : B= $\frac{3x-2}{x+1}$ làm hộ mk vớiiiii
Đáp án: $\text{B = $\dfrac{3x-2}{x+1}$ ∈ Z}$ $\text{ ĐKXĐ : x $\neq$ -1 }$ $\text{<=> $\dfrac{3x+3-5}{x+1}$ ∈ Z}$ $\text{<=>$\dfrac{3(x+1)-5}{x+1}$ ∈ Z}$ $\text{<=> 3 – $\dfrac{5}{x+1}$ ∈ Z}$ $\text{<=> x+1 chia hết cho 5}$ $\text{<=> x+1 ∈ Ư(5) }$ $\text{<=>x+1∈ {1 ; -1 ; 5; -5} }$ $\text{<=>x ∈ { 0 ; -2 ; 4 ; -6 }}$ Trả lời
ĐKXD : `x` $\neq$ `-1` `B∈Z` `⇔(3x-2)/(x+1) ∈ Z` `⇔(3x+3-5)/(x+1) ∈ Z` `⇔3 – 5/(x+1) ∈ Z` `⇔5/(x+1) ∈ Z` `⇔5` chia hết cho `x+1` `⇔x+1 ∈ Ư(5) ∈ {±1;±5}` `⇔x∈{0;-2;4;-6}` Trả lời
Đáp án:
$\text{B = $\dfrac{3x-2}{x+1}$ ∈ Z}$
$\text{ ĐKXĐ : x $\neq$ -1 }$
$\text{<=> $\dfrac{3x+3-5}{x+1}$ ∈ Z}$
$\text{<=>$\dfrac{3(x+1)-5}{x+1}$ ∈ Z}$
$\text{<=> 3 – $\dfrac{5}{x+1}$ ∈ Z}$
$\text{<=> x+1 chia hết cho 5}$
$\text{<=> x+1 ∈ Ư(5) }$
$\text{<=>x+1∈ {1 ; -1 ; 5; -5} }$
$\text{<=>x ∈ { 0 ; -2 ; 4 ; -6 }}$
ĐKXD : `x` $\neq$ `-1`
`B∈Z`
`⇔(3x-2)/(x+1) ∈ Z`
`⇔(3x+3-5)/(x+1) ∈ Z`
`⇔3 – 5/(x+1) ∈ Z`
`⇔5/(x+1) ∈ Z`
`⇔5` chia hết cho `x+1`
`⇔x+1 ∈ Ư(5) ∈ {±1;±5}`
`⇔x∈{0;-2;4;-6}`