Toán Lớp 6: 1.Tìm n a (3n+2):(2n-1)=-7 b (3n+2):(2n-1)=7 2.tìm n thuộc z a 3n-2:n+2 b 6n+5:2n-1 c 4n+3:3n+1 d 6n+3:4n-1 Làm chi tiết cho mình

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Toán Lớp 6:  1.Tìm n a (3n+2):(2n-1)=-7 b (3n+2):(2n-1)=7 2.tìm n thuộc z a  3n-2:n+2 b  6n+5:2n-1 c   4n+3:3n+1 d  6n+3:4n-1 Làm chi tiết cho mình nhé ,cảm ơn

daithanh · Answer

Lời giải và giải thích chi tiết:   1.   a) $(3n+2):(2n-1)=-7$   => $3n+2=-7(2n-1)$   => $3n+2=-14n+7$   => $3n+14n=7-2$   => $17n=5$   Vậy $n= frac{5}{17}$   b)    $(3n+2):(2n-1)=7$   => $3n+2=7(2n-1)$   => $3n+2=14n-7$   => $3n-14n=-7-2$   => $-11n=-9$   Vậy $n= frac{9}{11}$   2.    a) $3n-2 ⋮ n+2$     m&agrave; $3(n+2)  ⋮ n+2$ hay $3n+6  ⋮ n+2$     => $(3n-2)-(3n+6)  ⋮  n+2$     => $-8  ⋮ n+2$     => $n+2$ &isin; {$-8;-4;-2;-1;1;2;4;8$}     Vậy $n $&isin; {$-10;-6;-4;-3;-1;0;2;6$}     b) $6n+5  ⋮ 2n-1$     m&agrave; $3(2n-1) ⋮ 2n-1$ hay $6n-3 ⋮ 2n-1$     => $(6n+5)-(6n-3)  ⋮ 2n-1$     => $8 ⋮ 2n-1$     => $2n-1$&isin; {$-8;-4;-2;-1;1;2;4;8$}     => $2n$&isin;{$-7;-3;-1;0;2;3;5;9$}     => $n$&isin;{$ frac{-7}{2}; frac{-3}{2}; frac{-1}{2};0;1; frac{3}{2}; frac{5}{2}; frac{9}{2}$}     m&agrave; $n&isin;Z$     Vậy $n$&isin;{$0;1$}     c) $4n+3⋮3n+1$     =>$3(4n+3)⋮3n+1$     => $12n+9⋮3n+1$     m&agrave; $4(3n+1)⋮3n+1$ hay $12n+4⋮3n+1$     => $(12n+9)-(12n+4)⋮3n+1$     => $5⋮3n+1$     => $3n+1$&isin;{$-5;-1;1;5$}     => $3n$&isin;{$-6;-2;0;4$}     => $n$&isin;{$-2; frac{-2}{3};0; frac{4}{3}$}     m&agrave; $n&isin;Z$     Vậy $n$&isin;{$-2;0$}     d) $6n+3⋮4n-1$     => $2(6n+3)⋮4n-1$     => $12n+6⋮4n-1$     m&agrave; $3(4n-1)⋮4n-1$ hay $12n-3⋮4n-1$     => $(12n+6)-(12n-3)⋮4n-1$     => $9⋮4n-1$     => $4n-1$&isin;{$-9;-3;-1;1;3;9$}     => $4n$&isin;{$-8;-2;0;2;4;10$}     => $n$&isin;{$-2; frac{-1}{2};0; frac{1}{2};1; frac{5}{2}$}     m&agrave; $n&isin;Z$     Vậy $n$&isin;{$-2;0;1$}     @Deawoo     Xin c&acirc;u trả lời hay nhất