Toán tim n biet a,2n+9 chia het cho n-3 b,3n-1 chia het cho 3-2n 10/09/2021 By Margaret tim n biet a,2n+9 chia het cho n-3 b,3n-1 chia het cho 3-2n
b, Ta có: 3n-1$\vdots$3-2n ⇒-2.(3n-1)$\vdots$-2n+3 ⇒-6n+2$\vdots$-2n+3 ⇒3(-2n+3)-7$\vdots$-2n+3 ⇒-2n+3∈Ư(7)={1;7} -2n+3=1⇒n=… -2n+=7⇒n=… Vậy n∈{…} Trả lời
a) 2n+9 chia hết n-3
2(n-3) +15 chia hết n-3
n-3 thuộc Ư(15)
n=(4;2;18;-12;6;0;8;-2)
b, Ta có: 3n-1$\vdots$3-2n
⇒-2.(3n-1)$\vdots$-2n+3
⇒-6n+2$\vdots$-2n+3
⇒3(-2n+3)-7$\vdots$-2n+3
⇒-2n+3∈Ư(7)={1;7}
-2n+3=1⇒n=…
-2n+=7⇒n=…
Vậy n∈{…}