25 + 3 = ?
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Tính 25 . ( -3) = - 75
Suy ra kết quả:
(+25) . ( +3) = 75;
(-25) . ( -3) = 75;
(-25) . ( +3) = -75;
(+3) . ( -25) = -75
![](https://rs.olm.vn/images/avt/0.png?1311)
Tính 25 . ( -3) = - 75
Suy ra kết quả:
(+25) . ( +3) = 75;
(-25) . ( -3) = 75;
(-25) . ( +3) = -75;
(+3) . ( -25) = -75
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có
\(A=\dfrac{19}{25}\left(\dfrac{3}{7}+\dfrac{25}{19}\right)-\dfrac{3}{7}\left(\dfrac{19}{25}-\dfrac{7}{3}\right)\\ A=\dfrac{19}{25}.\dfrac{3}{7}+\dfrac{19}{25}.\dfrac{25}{19}-\dfrac{3}{7}.\dfrac{19}{25}+\dfrac{3}{7}.\dfrac{7}{3}\\ A=\dfrac{19}{25}.\dfrac{3}{7}-\dfrac{19}{25}.\dfrac{3}{7}+\dfrac{25}{9}.\dfrac{19}{25}+\dfrac{3}{7}.\dfrac{7}{3}\\ A=0+1+1\\ A=2\)
Vậy A= 2
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Xin phép đc ghi lại đề như sau \(C=\frac{19}{25}\left(\frac{3}{7}+\frac{25}{19}\right)-\frac{3}{7}\left(\frac{19}{25}-\frac{7}{3}\right)\)\(=\frac{19}{25}.\frac{3}{7}+\frac{19}{25}.\frac{25}{19}-\frac{3}{7}.\frac{19}{25}+\frac{3}{7}.\frac{7}{3}=\frac{19}{25}.\frac{3}{7}-\frac{3}{7}.\frac{19}{25}+\frac{19}{25}.\frac{25}{19}+\frac{3}{7}.\frac{7}{3}=0+1+1=2\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\dfrac{2}{9}+\dfrac{5}{9}=\dfrac{7}{9};\dfrac{5}{9}+\dfrac{2}{9}=\dfrac{7}{9}\)
Vậy: \(\dfrac{2}{9}+\dfrac{5}{9}=\dfrac{5}{9}+\dfrac{2}{9}\)
b) \(\dfrac{3}{25}+\dfrac{4}{25}+\dfrac{7}{25}=\dfrac{14}{25};\dfrac{3}{25}+\dfrac{7}{25}+\dfrac{4}{25}=\dfrac{14}{25}\)
Vậy: \(\dfrac{3}{25}+\dfrac{4}{25}+\dfrac{7}{25}=\dfrac{3}{25}+\dfrac{7}{25}+\dfrac{4}{25}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
25*7+25*3+25*4+25*6
= 25*(7+3+4+6)
= 25*20
= 25*10*2
= 250*2
= 500
25 + 3 = 28
#Hok tốt
28 nha cu !
# Linh