1.1/2x4x6+1/4x6x8+1/6x8x10+....+1/96x98x180
2.(1-3/4) x (1-3/7) x (1-3/10) x...x(1x3/97)x(1-3/100)
Ae giúp tôi, mai nộp r
1/2x4x6+1/4x6x8+1/6x8x10+......+1/50x52x54
\(\frac{1}{2.4.6}+\frac{1}{4.6.8}+\frac{1}{6.8.10}+..+\frac{1}{50.52.54}\)
\(=\frac{1}{4}.\left(\frac{1}{2.4}-\frac{1}{4.6}+\frac{1}{4.6}-\frac{1}{6.8}+....+\frac{1}{50.52}-\frac{1}{52.54}\right)\)
\(=\frac{1}{4}.\left(\frac{1}{2.4}-\frac{1}{52.54}\right)\)
\(=\frac{1}{4}.\frac{175}{1404}=\frac{175}{5616}\)
Tính tổng: 1/(2x4x6) + 1/(4x6x8) + 1/(6x8x10) +...+ 1/(96x98x100)
\(=\frac{49\times50-1}{4\times98\times100}\)
Đề bài như sau:
1/2x4x6+1/4x6x8+1/6x8x10+1/8x10x12+1/10x12x14+...+1/96x98x100
Giups mình nhé các bạn,mình đang cần cực gấp(khoảng 10 p nữa phải nộp rùi T_T)
Xin các bạn giúp mình.
Cảm ơn các bạn rất nhiều.
Tính nhanh
1/2x4x6 +1/4x6x8 + 1/6x8x10 + 1/8x10x12 + ...+ 1/96x98x100
Đặt biểu thức là A
\(4xA=\frac{4}{2x4x6}+\frac{4}{4x6x8}+\frac{4}{6x8x10}+\frac{4}{8x10x12}+...+\frac{4}{94x96x98}+\frac{4}{96x98x100}\)
\(4xA=\frac{6-2}{2x4x6}+\frac{8-4}{4x6x8}+\frac{10-6}{6x8x10}+\frac{12-8}{8x10x12}+...+\frac{98-94}{94x96x98}+\frac{100-96}{96x98x100}\)
\(4xA=\frac{1}{2x4}-\frac{1}{4x6}+\frac{1}{4x6}-\frac{1}{6x8}+\frac{1}{6x8}-\frac{1}{8x10}+...+\frac{1}{94x96}-\frac{1}{96x98}+\frac{1}{96x98}-\frac{1}{98x100}\)
\(4xA=\frac{1}{2x4}-\frac{1}{98x100}=\frac{49x50-1}{98x100}\Rightarrow A=\frac{49x50-1}{4x98x100}\)
Bài 1: Tính nhanh
a) (1-1/2) x (1-1/3)x (1-1/4) x (1-1/5)
b) (1-3/4) x (1-3/7) x (1-3/10) x (1-3/13)x...x (1-3/97) x (1-3/100)
Các anh các cj giúp em vs ạ
Các anh các cj giúp em nhé
Em cảm ơn trước
Giải:
a) \(\left(1-\dfrac{1}{2}\right).\left(1-\dfrac{1}{3}\right).\left(1-\dfrac{1}{4}\right).\left(1-\dfrac{1}{5}\right)\)
\(=\dfrac{1}{2}.\dfrac{2}{3}.\dfrac{3}{4}.\dfrac{4}{5}\)
\(=\dfrac{1.2.3.4}{2.3.4.5}\)
\(=\dfrac{1}{5}\)
b) \(\left(1-\dfrac{3}{4}\right).\left(1-\dfrac{3}{7}\right).\left(1-\dfrac{3}{10}\right).\left(1-\dfrac{3}{13}\right).....\left(1-\dfrac{3}{97}\right).\left(1-\dfrac{3}{100}\right)\)
\(=\dfrac{1}{4}.\dfrac{4}{7}.\dfrac{7}{10}.\dfrac{10}{13}.....\dfrac{94}{97}.\dfrac{97}{100}\)
\(=\dfrac{1.4.7.10.....94.97}{4.7.10.13.....97.100}\)
\(=\dfrac{1}{100}\)
Chúc bạn học tốt!
A)
\(\left(1-\dfrac{1}{2}\right)x\left(1-\dfrac{1}{3}\right)x\left(1-\dfrac{1}{4}\right)x\left(1-\dfrac{1}{5}\right)\)
\(=\dfrac{1}{2}x\dfrac{1}{3}x\dfrac{1}{4}x\dfrac{1}{5}\)
\(=\dfrac{1x2x3x4}{2x3x4x5}\)
\(=\dfrac{1}{5}\)
B)
\(\left(1-\dfrac{3}{4}\right).\left(1-\dfrac{3}{7}\right).\left(1-\dfrac{3}{10}\right)......\left(1-\dfrac{3}{97}\right).\left(1-\dfrac{3}{100}\right)\)
\(\dfrac{1}{4}.\dfrac{1}{7}.....\dfrac{94}{97}.\dfrac{97}{100}\)
\(\dfrac{1}{100}\)
học tốt nhé!!!
1/2x4x6+1/4x6x8+1/6x8x10+........+1/50x52x54
giai bai tinh nhanh nay ra cho minh nhe
tính nhanh
a (1-1/2) x (1-1/3) x (1-1/4) x (1-1/5)
b (1-3/4)x ( 1-3/7) x ( 1-3/10) x (1-3/13) x...x (1-3/97) x (1-3/100)
`a)(1-1/2)xx(1-1/3)xx(1-1/4)xx(1-1/5)`
`=1/2xx2/3xx3/4xx4/5`
`=[1xx2xx3xx4]/[2xx3xx4xx5]`
`=1/5`
`b)(1-3/4)xx(1-3/7)xx(1-3/10)xx(1-3/13)xx .... xx(1-3/97)xx(1-3/100)`
`=1/4xx4/7xx7/10xx10/13xx .... xx94/97xx97/100`
`=[1xx4xx7xx10xx...xx94xx97]/[4xx7xx10xx13xx....xx97xx100]`
`=1/100`
Tính bằng cách thuận tiện:
(1-\(\dfrac{3}{4}\)) x (1 - \(\dfrac{3}{7}\)) x (1 - \(\dfrac{3}{10}\)) x (1 - \(\dfrac{3}{13}\)) x ....... x (1 - \(\dfrac{3}{97}\)) x (1 - \(\dfrac{3}{100}\))
Giải:
\(\left(1-\dfrac{3}{4}\right).\left(1-\dfrac{3}{7}\right).\left(1-\dfrac{3}{10}\right).\left(1-\dfrac{3}{13}\right).....\left(1-\dfrac{3}{97}\right).\left(1-\dfrac{3}{100}\right)\)
\(=\dfrac{1}{4}.\dfrac{4}{7}.\dfrac{7}{10}.\dfrac{10}{13}.....\dfrac{94}{97}.\dfrac{97}{100}\)
\(=\dfrac{1.4.7.10.....94.97}{4.7.10.13.....97.100}\)
\(=\dfrac{1}{100}\)
Bài 12 : Tính nhanh
a) (1-3/4) x (1-3/7) x (1-3/10) x (1-1/13) x ........ x (1- 3/97) x ( 1-3/100)
#)Giải :
\(\left(1-\frac{3}{4}\right)x\left(1-\frac{3}{7}\right)x\left(1-\frac{3}{10}\right)x\left(1-\frac{1}{13}\right)x...x\left(1-\frac{3}{100}\right)\)
\(=\frac{1}{4}x\frac{4}{7}x\frac{7}{10}x...x\frac{94}{97}x\frac{97}{100}\)
\(=\frac{1x4x7x...x94x100}{4x7x10x...x97x100}\)
\(=\frac{1}{100}\)
#~Will~be~Pens~#
\(\left(1-\frac{3}{4}\right)\left(1-\frac{3}{7}\right)\left(1-\frac{3}{10}\right)\left(1-\frac{1}{13}\right)...\left(1-\frac{1}{97}\right)\left(1-\frac{3}{100}\right)\)
\(=\frac{1}{4}.\frac{4}{7}.\frac{7}{10}.\frac{10}{13}...\frac{94}{97}.\frac{97}{100}\)
\(=\frac{1}{100}\)
\(\left(1-\frac{3}{4}\right)\left(1-\frac{3}{7}\right)\left(1-\frac{3}{10}\right)....\left(1-\frac{3}{100}\right)\)
\(\frac{1}{4}.\frac{4}{7}.\frac{7}{10}....\frac{94}{97}.\frac{97}{100}\)
Rút gọn đi (gạch chéo ý)
\(=\frac{1}{100}\)
Chúc bạn học tốt !!!