Question

Tính

A=13/21.2/11+13/21.9/11+8/21.     

B=(1-1/5).(1-2/5).(1-3/5)...(1-9/5)

C= (1-1/2).(1-1/3).(1-1/4)...(1-1/50)

D= 2²/1.3 .  3²/2.4 . 4²/3.5  . 5²/4.6 . 6²/5.7

Answer 1

A = 13/21.2/11 + 13/21.9/11 + 8/21
= (13/21) + (13/21) + (8/21)
= (13 + 13 + 8)/21
= 34/21

B = (1 - 1/5)(1 - 2/5)(1 - 3/5)...(1 - 9/5)
= (4/5)(3/5)(2/5)(1/5)(0/5)(-1/5)(-2/5)(-3/5)(-4/5)
= 0

C = (1 - 1/2)(1 - 1/3)(1 - 1/4)...(1 - 1/50)
= (1/2)(2/3)(3/4)(4/5)...(49/50)
= 1/50

D = (2^2/1.3) * (3^2/2.4) * (4^2/3.5) * (5^2/4.6) * (6^2/5.7)
= (4/3) * (9/8) * (16/15) * (25/23) * (36/35)
= 0.979