Tính 25 . ( -3) = - 75
Suy ra kết quả:
(+25) . ( +3) = 75;
(-25) . ( -3) = 75;
(-25) . ( +3) = -75;
(+3) . ( -25) = -75
Tính 25 . ( -3) = - 75
Suy ra kết quả:
(+25) . ( +3) = 75;
(-25) . ( -3) = 75;
(-25) . ( +3) = -75;
(+3) . ( -25) = -75
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