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

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1. Đáp án:

    

   Giải thích các bước giải:

    $3$ $\vdots$ $n+1$

   $⇒n+1∈${$3;1;-1;-3$}

   $⇒n∈${$2;0;-2;-4$}

   $ $

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

   $⇒2n+5∈${$10;5;2;1;-1;-2;-5;-10$}

   $⇒2n∈${$5;0;-3;-4;-6;-7;-10;-15$}

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

   $ $

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

   $⇒n-1∈${$11;1;-1;-11$}

   $⇒n∈${$12;2;0;-10$}

   $ $

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

   $⇒(n-5).(n-5-2)+7$ $\vdots$ $n-5$

   $⇒7$ $\vdots$ $n-5$

   $⇒n-5∈${$7;1;-1;-7$}

   $⇒n∈${$12;6;4;-2$}

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