Đáp án:
._.
Giải thích các bước giải:
Gọi ` ƯC` nguyên tố `( 18n + 3; 21n + 7 )` là `d`Ta có: $\begin{cases} 18n + 3 \vdots d \\ 21n + 7 \vdots d \end{cases}$`=>` $\begin{cases} 7 ( 18n + 3 ) \vdots d \\ 6 ( 21n + 7 ) \vdots d \end{cases}$`=>` $\begin{cases} 126n + 21 \vdots d \\ 126n + 42 \vdots d \end{cases}$`=> ( 126n + 42 ) – ( 126n + 21 ) \vdots d ``=> 21 \vdots d``=> d = 3; 7`Có: `21n + 7` $\not{\vdots}$ `3 (` vì `21n \vdots 3; 7` $\not{\vdots}$ `3 ) ``=> d = 7`Có: `18n + 3 vdots 7``=> 21n – 3n + 3 vdots 7``=> -3 ( n – 1 ) vdots 7``=> n – 1 vdots 7 ``=> n – 1 = 7k ( k in ZZ)``=> n = 7k + 1`Vậy `n = 7k + 1 `
Đáp án: n=7k-1
Gọi các ước nguyên tố chung của tử và mẫu là a
=> 18n+3 chia hết cho a=>7.(18n+3)chia hết cho a
=>24n+7chia hết cho a =>6.(24n+7)chia hết cho a
=>6.(24n+7)-7(18n+3)chia hết cho a
(=)21 chia hết cho a=>a thuộc {3;7}
TH1:a=3 (21n+7 ko chia hết cho 3) LOẠI
TH2:a=7=>18n +3-21chia hết cho a
(=)18n-18 chia hết cho a
(=)18.(n-1)chia hết cho a=>n-1 chia hết cho a
(=)n=7k+1
vậy n=7k-1
cho a-b+c=2 a^2+b^2+c^2=4 x/a=-y/b=z/c CMR xy+yz+zx=0
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Giúp mik vs mình đag cần gấp ! Cảm ơn các bạn nhìu
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Tại sao nói nỗi buồn trong bài thơ "Tràng Giang" trong sáng, có ý nghĩa?
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Giúp mình vs mình đag cần gấp ! ;-;
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