K
Khách
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Các câu hỏi dưới đây có thể giống với câu hỏi trên
4 tháng 8 2016
A = 3/1×5 + 3/5×9 + 1/9×13 + ... + 9/97×101 + 3/101×105
A = 3/4 × (4/1×5 + 4/5×9 + 4/9×13 + ... + 4/97×101 + 4/101×105)
A = 3/4 × (1 - 1/5 + 1/5 - 1/9 + 1/9 - 1/13 + ... + 1/97 - 1/101 + 1/101 - 1/105)
A = 3/4 × (1 - 1/105)
A = 3/4 × 104/105
A = 26/35
B = 1/5 + 1/25 + 1/125 + 1/625 + 1/3125 + 1/15625
5B = 1 + 1/5 + 1/25 + 1/125 + 1/625 + 1/3125
5B - B = (1 + 1/5 + 1/25 + 1/125 + 1/625 + 1/3125) - (1/5 + 1/25 + 1/125 + 1/625 + 1/3125 + 1/15625)
4B = 1 - 1/15625
4B = 15624/15625
B = 15624/15625 : 4
B = 3906/15625
C = 1 + 2 + 4 + 8 + 16 + ... + 2048 + 4096
2C = 2 + 4 + 8 + 16 + 32 + ... + 4096 + 8192
2C - C = (2 + 4 + 8 + 16 + 32 + ... + 4096 + 8192) - (1 + 2 + 4 + 8 + ... + 2048 + 4096)
B = 8192 - 1
B = 8191
CN
2
C
2 tháng 12 2023
A = 3+ 3/5+ 3/25+ 3/125+ 3/625
A = 3/1+ 3/5+ 3/25+ 3/125+ 3/625
A = 1875/625 + 375/625 + 75/625 + 15/625 + 3/625
A = 3 + 0,6 + 0,12 + 0,024 + 0,0048
A = 3,6 + 0,12 + 0,024 + 0,0048
A = 3,72 + 0,024 + 0,0048
A = 3,744 + 0,0048
A = 3,7488
NT
Nguyễn Thị Thương Hoài
Giáo viên
VIP
2 tháng 12 2023
A = 3 + \(\dfrac{3}{5}\) + \(\dfrac{3}{25}\) + \(\dfrac{3}{125}\) + \(\dfrac{3}{625}\)
5\(\times\)A = 15 + 3 + \(\dfrac{3}{5}\) + \(\dfrac{3}{25}\) + \(\dfrac{3}{125}\)
5 \(\times\) A - A = 15 + 3 + \(\dfrac{3}{5}\) + \(\dfrac{3}{25}\) + \(\dfrac{3}{125}\) - (3 + \(\dfrac{3}{5}\) + \(\dfrac{3}{25}\) + \(\dfrac{3}{125}\) + \(\dfrac{3}{625}\))
4 \(\times\) A = 15 + 3 + \(\dfrac{3}{5}\) + \(\dfrac{3}{25}\) + \(\dfrac{3}{125}\) - 3 - \(\dfrac{3}{5}\) - \(\dfrac{3}{25}\) - \(\dfrac{3}{125}\) - \(\dfrac{3}{165}\)
4 \(\times\) A = (15 - \(\dfrac{3}{625}\)) + (3 - 3) + (\(\dfrac{3}{5}\) - \(\dfrac{3}{5}\)) + (\(\dfrac{3}{25}-\dfrac{3}{25}\)) + (\(\dfrac{3}{125}\)-\(\dfrac{3}{125}\))
4 \(\times\) A = \(\dfrac{9372}{625}\)
A = \(\dfrac{9372}{625}\) : 4
A = \(\dfrac{2343}{625}\)
9 tháng 7 2016
Đặt \(A=3+\frac{3}{5}+\frac{3}{25}+\frac{3}{125}+\frac{3}{625}\)
\(5A=15+3+\frac{3}{5}+\frac{3}{25}+\frac{3}{125}\)
\(5A-A=\left(15+3+\frac{3}{5}+\frac{3}{25}+\frac{3}{125}\right)-\left(3+\frac{3}{5}+\frac{3}{25}+\frac{3}{125}+\frac{3}{625}\right)\)
\(4A=15-\frac{3}{625}\)
\(A=\frac{15-\frac{3}{625}}{4}\)
Ủng hộ mk nha ^_-
Ta thấy: \(3=3\times\frac{625}{625}=625\times\frac{3}{625}\)
\(\frac{3}{5}=\frac{3}{5}\times\frac{125}{125}=\frac{3\times125}{625}=125\times\frac{3}{625}\)
\(\frac{3}{25}=\frac{3}{25}\times\frac{25}{25}=\frac{3\times25}{625}=25\times\frac{3}{625}\)
\(\frac{3}{125}=\frac{3}{125}\times\frac{5}{5}=\frac{3\times5}{625}=5\times\frac{3}{625}\)
Từ đó, suy ra : \(3+\frac{3}{5}+\frac{3}{25}+\frac{3}{125}+\frac{3}{625}\)
\(=625\times\frac{3}{625}+125\times\frac{3}{625}+25\times\frac{3}{625}+5\times\frac{3}{625}+\frac{3}{625}\)
\(=\frac{3}{625}\left(625+125+25+5+1\right)\)
\(=\frac{3}{625}\times781\)
\(=\frac{2343}{625}\)
thank