tính :
1 / 2 + 1 / 4 + 1 / 8 + ..... + 1 / 128 + 1 / 256
Tính:
A= 1/2+1/4+1/8+1/16+1/64+1/128+1/256
A = \(\dfrac{1}{2}\) + \(\dfrac{1}{4}\) + \(\dfrac{1}{8}\) + \(\dfrac{1}{16}\) + \(\dfrac{1}{64}\) + \(\dfrac{1}{128}\) + \(\dfrac{1}{256}\)
2A = 1 + \(\dfrac{1}{2}\) + \(\dfrac{1}{4}\) + \(\dfrac{1}{8}\) + \(\dfrac{1}{16}\) + \(\dfrac{1}{64}\) + \(\dfrac{1}{128}\)
2A - A = 1 - \(\dfrac{1}{256}\)
A = \(\dfrac{255}{256}\)
tính :
1 / 2 + 1 / 4 + 1 / 8 + ..... + 1 / 128 + 1 / 256
Tính nhanh
1/2 + 1/4 + 1/8 +................ + 1/128 + 1/256
A= 1/2 + 1/4+ 1/8+ 1/16 + 1/32 + 1/64 + 1/128 + 1/256 + 1/512
A = 1 - 1/2 + 1/2- 1/4 + 1/4 - 1/8 + 1/8 - 1/16 + 1/16 - 1/32 + 1/32 - 1/64 + 1/64 - 1/128 + 1/128 - 1/256 - 1/256 - 1/512
A = 1 - 1/512
A = 511/512
dựa vào nhé
A = 1 - 1/2 + 1/2 - 1/4 + 1/4 - 1/8 + ..... + 1/64 - 1/128 + 1/128 -1/256
= 1 - 1/256 = 255/256
Tính nhanh : 1+1/2+1/4+1/8+1/16+1/32+1/64+1/128+1/256+1/512
Tính nhanh
1/2+1/4+1/8+1/16+1/32+1/64+1/128+1/256
Tính nhanh:
1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 + 1/256
1/2 + 1/4+ 1/8+ 1/16 + 1/32 + 1/64 + 1/128 + 1/256 + 1/512
= 1 – 1/2 + 1/2- 1/4 + 1/4 – 1/8 + 1/8 – 1/16 + 1/16 – 1/32 + 1/32 – 1/64 + 1/64 – 1/128 + 1/128 – 1/256 – 1/256 – 1/512
= 1 – 1/512
= 511/512 .
Câu hỏi của Speed of light - Toán lớp 4 - Học toán với OnlineMath
Em tham khảo bài đc OLM k đúng nhé!
Cảm ơn các bạn
Tính nhanh
1/2+1/4+1/8+1/18+1/32+1/64+1/128+1/256
Đặt A
A= 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 + 1/256
2A= 2(1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 + 1/256)
= 1+1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128
=>A = 2A-A =1+1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 -1/2 - 1/4 - 1/8 - 1/16 - 1/32 - 1/64 - 1/128 - 1/256
=1-1/256
=255/256
Chúc học tốt
Đặt A = 1/2+1/4+1/8+1/18+1/32+1/64+1/128+1/256
=> 2A = 1+1/2+1/4+1/8+1/18+1/32+1/64+1/128
=>2A - A = 1 - 1/256
=> A = 255/256
1/2+1/4+1/8+1/18+1/32+1/64+1/128+1/256 \(=\frac{2279}{2304}\)
nha bạn ^_^
le thi minhtính bằng cách thuận tiện nhất:
1/2+1/4+1/8+1/16+1/32+1/64+1/128+1/256
Đặt A = 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 + 1/256
=> 2A = 1 + 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128
=> 2A - A = (1 + 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128) - (1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 + 1/256)
=> A = 1 - 1/256
=> A = 255/256
Vậy: ...
Bài 1: Tính nhanh
S = 1 + 1/2 + 1/4 + 1/8 + ..................... + 1/128 + 1/256
S = 1 + 1/2 + 1/4 + 1/8 + .....................1/128 + 1/256
= 1 + (1 – 1/2) + (1/2 – 1/4) + (1/4 – 1/8) + ....................... (1/128 – 1/256)
= 2 – 1/256 = 511/256
Vậy S = 511/256