a: \(\Leftrightarrow n+2\in\left\{1;-1;5;-5\right\}\)

hay \(n\in\left\{-1;-3;3;-7\right\}\)

b: \(\Leftrightarrow n-1-2⋮n-1\)

\(\Leftrightarrow n-1\in\left\{1;-1;2;-2\right\}\)

hay \(n\in\left\{2;0;3;-1\right\}\)

c: \(\Leftrightarrow3n-6+8⋮n-2\)

\(\Leftrightarrow n-2\in\left\{1;-1;2;-2;4;-4;8;-8\right\}\)

hay \(n\in\left\{3;1;4;0;6;-2;10;-6\right\}\)

abc + ab + a = 127

a x 111 + b x 11 + c = 127

=> a = 1 (a không thể = 0 vì b x 11 + c chỉ lớn nhất là 108)

111 + b x 11 + c = 127

b x 11 + c = 127 - 111 

b x 11 + c = 16

=> b = 1 ; c  = 5 thoả mãn

Số cần tìm là 115

Số đó là : 115 nha

Mình trả lời đầu tiên

it was pouring with rain down there
she would come and see me on Friday if that was all right
club had lost quite a lot of money the previous month
she would have finished writing the report by the time I got there
she had enjoyed herself the previous night
what the most interesting sights were
if I had got a town plan
where they could stay
how long the film lasted
if there were guided tours
which way the castle was
Nick to stay for lunch
Martin to see a doctor
for having caused so much trouble
going out for the day
to do the washing up
to post the letter
having made a mistake
Mike not to touch the electric wires
if I were taking much money with me to France

Ét ô ét~

100 x a + 10 x b + c + 10 x a + b + a = 507

111 x a + 11xb + c = 507

a = 4

11xb + c = 507 - 444

11 x b + c = 63 = 11 x 5 + 8

vậy: b = 5 và c = 8

Số cần tìm: 458

Ta có

100 x a + 10 x b + c + 10 x a + b + a = 732

111 x a + 11 x b + c = 732

=> a = 6

11 x b + c = 732 - 666

11 x b + c = 66 = 11 x 6 + 0

Vậy b = 6, c = 0

Vậy số cần tìm là 660

 a=6

b=6

c=0

Ta có : abc + ab+a =732

=> 100a + 10b +c +10a + b+a=732

=> 111a + 11b + c = 732 

Khi đó ta thấy : 

<=> 111a < 732 => a < 7 

Lại có : 11b + c < 11.10 + 10 

=> 11b + c < 120 nên 111a > 732 - 120

=> 111a > 612 => a > 5 

<=> a = 6 

Vì a = 6 => 666 + 11b + c = 732

=> 11b + c = 732 - 666

=> 11b + c = 66 => 11b < 66 => b < 6 mà c < 10 nên 11b > 56 => b > 4

<=> b = 5 và c = 9 

$\Rightarrow$abc = 659

TL:

9/21;10/21;11/21;12/21