Question

Rút gọn các phân số sau:

a)\(\dfrac{-315}{540}\) b) \(\dfrac{25.13}{26.35}\) c) \(\dfrac{3.13-13.18}{15.40-80}\)

Answer 1

Rút gọn các phân số sau:

a, \(\dfrac{-315}{540}\) = \(\dfrac{-315:45}{540:45}\) = \(\dfrac{-7}{12}\)

b, \(\dfrac{25.13}{26.35}\) = \(\dfrac{5.5.13}{13.2.5.7}\) = \(\dfrac{5}{2.7}\) = \(\dfrac{5}{14}\)

c, \(\dfrac{3.13-13.18}{15.40-80}\) = \(\dfrac{3.13-13.18}{15.40-2.40}\) = \(\dfrac{13.\left(3-18\right)}{40.\left(15-2\right)}\)

= \(\dfrac{13.\left(-15\right)}{40.13}\) = \(\dfrac{-3}{8}\)

Answer 2

a) \(\dfrac{-315}{540}=\dfrac{-315:45}{540:45}=\dfrac{-7}{12}\)

b) \(\dfrac{25\cdot13}{26\cdot35}=\dfrac{5\cdot5\cdot13}{2\cdot13\cdot5\cdot7}=\dfrac{5}{2\cdot7}=\dfrac{5}{14}\)

c) \(\dfrac{3\cdot13-13\cdot18}{15\cdot40-80}=\dfrac{3\cdot13-13\cdot18}{15\cdot40-2\cdot40}=\dfrac{13\cdot\left(3-18\right)}{40\left(15-2\right)}=\dfrac{13\cdot\left(-15\right)}{40\cdot13}=\dfrac{1\cdot\left(-3\right)}{8\cdot1}=\dfrac{-3}{8}\)