ko khó, nhưng lâu lắm

b) Ta có: A = \(\dfrac{1946}{1986}\) = \(1-\dfrac{40}{1986}\)

B = \(\dfrac{1968}{2008}\) = \(1-\dfrac{40}{2008}\)

Vì \(\dfrac{40}{1986}\) > \(\dfrac{40}{2008}\) ( Do 1968 < 2008)

=> \(1-\dfrac{40}{1986}\) < \(1-\dfrac{40}{2008}\)

=> A < B

P/s: Hơi muộn nhỉ!!!! ( do bây giờ mới rảnh để trả lời )

Câu 5:

a) Dễ lắm!!!

Ta có: A = \(\left(1-\dfrac{1}{2010}\right)\) . \(\left(1-\dfrac{2}{2010}\right)\) .... \(\left(1-\dfrac{2011}{2010}\right)\)

=> A = \(\left(1-\dfrac{1}{2010}\right)\). \(\left(1-\dfrac{2}{2010}\right)\) .....\(\left(1-\dfrac{2010}{2010}\right)\)\(\left(1-\dfrac{2011}{2010}\right)\) ( ghi hàng này cho em hiểu thôi chứ ko cần)

=> A = \(\left(1-\dfrac{1}{2010}\right)\) ......(1-1)\(\left(1-\dfrac{2011}{2010}\right)\)

=> A = \(\left(1-\dfrac{1}{2010}\right)\) .....0. \(\left(1-\dfrac{2011}{2010}\right)\) = 0

hãy search trên google