a) 3 ⁞ ( n + 1) b) 10 ⁞ ( 2n + 5) b) c) -11 ⁞ ( n – 1) d) ( n – 5)2 – 2.(n – 5) + 7 ⁞ (n – 5)

Đáp án:

Giải thích các bước giải:

 $3$ $\vdots$ $n+1$

$⇒n+1∈${$3;1;-1;-3$}

$⇒n∈${$2;0;-2;-4$}

$ $

$10$ $\vdots$ $2n+5$

$⇒2n+5∈${$10;5;2;1;-1;-2;-5;-10$}

$⇒2n∈${$5;0;-3;-4;-6;-7;-10;-15$}

$⇒n∈${$\dfrac{5}{2};0;\dfrac{-3}{2};-2;-3;\dfrac{-7}{2};-5;\dfrac{-15}{2}$}

$ $

$-11$ $\vdots$ $n-1$

$⇒n-1∈${$11;1;-1;-11$}

$⇒n∈${$12;2;0;-10$}

$ $

$(n-5)^{2}-2.(n-5)+7$ $\vdots$ $n-5$

$⇒(n-5).(n-5-2)+7$ $\vdots$ $n-5$

$⇒7$ $\vdots$ $n-5$

$⇒n-5∈${$7;1;-1;-7$}

$⇒n∈${$12;6;4;-2$}