Đáp án:
Ta có :(n+7)²-(n-5)²=(n+7+n-5)(n+7-n+5)=12.(2n+2)=12.2.(n+1)=24(n+1)
vì n là số nguyên ⇒24.(n+1) chia hết cho 24
Vậy (n+7)²-(n-5)² chia hết cho 24
Nhớ vote 5 sao cho mk nha :))
Giải thích các bước giải:
$(n+7)^2-(n-5)^2$
$=(n+7-n+5)(n+7+n-5)$
$=12.(2n+2)$
$=12.2(n+1)$
$=24.(n+1)$
$24\vdots24 ⇒ 24(n+1)\vdots24$
$\text{Hay $(n+7)^2-(n-5)^2\vdots24$ (đpcm).}$
chúc em học tốt.
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Mn giúp mk bài này nhanh với!!!
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Vẽ bt21 ít nhất 3 con nhé !!!!!!!!!!!!!!!!!!!!!!!!!
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Vẽ nobita nhé !
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