biết m +n=25 tính:3.m+5.n+2.m+n+m
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![](https://rs.olm.vn/images/avt/0.png?1311)
3m + 5n + 2 + m + n + m = 3m + 3n + 2n + 2 + m + n + m = (3m + 3n) + (2m + 2m) + (2 + n) = 3(m + n) + 2(m + n) + (2 + n) = 3.25 + 2.25 + 2 + n = 125 + 2 + n = 127 + n
tick đúng nha
3m + 5n + 2 + m + n + m = 3m + 3n + 2n + 2 + m + n + m = (3m + 3n) + (2m + 2m) + (2 + n) = 3(m + n) + 2(m + n) + (2 + n) = 3.25 + 2.25 + 2 + n = 125 + 2 + n = 127 + n
![](https://rs.olm.vn/images/avt/0.png?1311)
3 x m + 5 x n +2 x m + n + m
=3 x m +5 x n + 2 x m + n x 1 + m x 1
=m x (3 + 2 + 1) + n x (5 + 1)
=m x 6 + n x 6
=6 x ( m + n)
=6 x 25
=150
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có :
\(M=5+5^2+5^3+...+5^{60}\)
\(\Leftrightarrow\)\(5M=5^2+5^3+5^4+...+5^{61}\)
\(\Leftrightarrow\)\(5M-M=\left(5^2+5^3+5^4+...+5^{61}\right)-\left(5+5^2+5^3+...+5^{60}\right)\)
\(\Leftrightarrow\)\(4M=5^{61}-5\)
\(\Leftrightarrow\)\(M=\frac{5^{61}-5}{4}\)
Vậy \(M=\frac{5^{61}-5}{4}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a)Ta có:
\(\left(n+5\right)⋮\left(n-1\right)\)
\(\Rightarrow\left(n-1+6\right)⋮\left(n-1\right)\)
\(\Rightarrow6⋮\left(n-1\right)\)
Ta có bảng sau:
\(n-1\) | -6 | -3 | -2 | -1 | 1 | 2 | 3 | 6 |
n | -5 | -2 | -1 | 0 | 2 | 3 | 4 | 7 |
TM | TM | TM | TM | TM | TM | TM | TM |
b)\(\left(2n-4\right)⋮\left(n+2\right)\)
\(\Rightarrow\left(2n+4-8\right)⋮\left(n+2\right)\)
\(\Rightarrow8⋮\left(n+2\right)\)
Ta có bảng sau:
n+2 | -8 | -4 | -2 | -1 | 1 | 2 | 4 | 8 |
n | -10 | -6 | -4 | -3 | -1 | 0 | 2 | 6 |
TM | TM | TM | TM | TM | TM | TM | TM |
c)Ta có:
\(\left(6n+4\right)⋮\left(2n+1\right)\)
\(\Rightarrow\left(6n+3+1\right)⋮\left(2n+1\right)\)
\(\Rightarrow1⋮\left(2n+1\right)\)
Ta có bảng sau:
2n+1 | -1 | 1 |
2n | -2 | 0 |
n | -1 | 0 |
d)Ta có:
\(\left(3-2n\right)⋮\left(n+1\right)\)
\(\Rightarrow\left(-2n-2+5\right)⋮\left(n+1\right)\)
\(\Rightarrow5⋮\left(n+1\right)\)
Ta có bảng sau:
n+1 | -5 | -1 | 1 | 5 |
n | -6 | -2 | 0 | 4 |
![](https://rs.olm.vn/images/avt/0.png?1311)
Nếu m = 10, n = 5 , p = 2 thì
m + n + p = 10 + 5 + 2 = 17
m + ( n + p) = 10 + ( 5 + 2) = 17
m - n - p = 10 - 5 - 2 = 3
m - ( n + p )= 10 - (5 + 2) = 3
m + n x p = 10 + 5 x 2 = 20
(m + n) x p = ( 10 + 5 ) x 2 = 30
![](https://rs.olm.vn/images/avt/0.png?1311)
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3 x m + 5 x n + 2 x m + n +m
=3 x m + 5 x n + 2 x m +n x 1 + m x 1
=m x (2+3+1) +n x (5 +1 )
=m x 6 + n x 6
=6 x( m + n)
=6 x 25
= 150
ai đồng ý không