1/2+(16/21+27/13)-(14/12-5/21) tính hợp lý kết quả đúng là (94/39)

Giải :

$\dfrac{1}{2}+$$(\dfrac{16}{21}+$$\dfrac{27}{13})-($$\dfrac{14}{12}-$$\dfrac{5}{21}$

$=\dfrac{1}{2}+$$\dfrac{16}{21}+$$\dfrac{27}{13}-$$\dfrac{14}{12}+$$\dfrac{5}{21}$

$=(\dfrac{16}{21}+$$\dfrac{5}{21})+($$\dfrac{1}{2}-$$\dfrac{14}{12})$$+\dfrac{27}{13}$

$=1+\dfrac{-2}{3}+$$\dfrac{27}{13}$

$=\dfrac{1}{3}+$$\dfrac{27}{13}$

$=\dfrac{94}{39}$