Question

tính bằng cách thuận tiện nhất :

a, 13/19 x 23/11 - 13/19 x 8/11 - 13/ 19 x 4/11

Answer 1

13/19 x 23/11 - 13/19 x 8/11 - 13/19 x 4/11

= 13/19 x (23/11 - 8/11 - 4/11)

= 13/19 x 1

= 13/19

Answer 2

\(\dfrac{13}{19}\times\dfrac{23}{11}-\dfrac{13}{19}\times\dfrac{8}{11}-\dfrac{13}{19}\times\dfrac{4}{11}\\ =\dfrac{13}{19}\times\left(\dfrac{23}{11}-\dfrac{8}{11}-\dfrac{4}{11}\right)\\ =\dfrac{13}{19}\times1=\dfrac{13}{19}\)

Answer 3

câu b, 20/5x7 + 20/7x9 + 20/ 9 x11 + ..... 20 / 33 x35

Answer 4

\(\dfrac{13}{19}\cdot\dfrac{23}{11}-\dfrac{13}{19}\cdot\dfrac{8}{11}-\dfrac{13}{19}\cdot\dfrac{4}{11}\)

\(=\dfrac{13}{19}\left(\dfrac{23}{11}-\dfrac{8}{11}-\dfrac{4}{11}\right)\)

\(=\dfrac{13}{19}\)