1-3/4*1-3/7*1-3/10*1-3/13*............*1-3/97*1-3/100
(1-3/4)*(1-3/7)*(1-3/10)*(1-3/13)*........*(1-3/97)*(1-3/100)
(1-3/4)(1-3/7)(1-3/10)(1-3/13)....(1-3/97)(1-3/100) = ?
\(\left(1-\frac{3}{4}\right)\left(1-\frac{3}{7}\right)\left(1-\frac{3}{10}\right)...\left(1-\frac{3}{97}\right)\left(1-\frac{3}{100}\right)\)
\(=\frac{1}{4}.\frac{4}{7}.\frac{7}{10}.....\frac{94}{97}.\frac{97}{100}\)
\(=\frac{1.4.7.....94.97}{4.7.10.....97.100}\)
\(=\frac{1}{100}\)
Tính tổng:a) (1-1/2).(1-1/3).(1-1/4).(1-1/5)
b)(1-3/4).(1-3/7).(1-3/10).(1-3/13)...(1-3/97).(1-3/100)
2) Chứng minh)1/3+1/7+1/13+1/21+...+1/73+1/97<1
a) \(\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right).\left(1-\frac{1}{5}\right)\)
\(=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.\frac{4}{5}\)
\(=\frac{1}{5}\)
b) \(\left(1-\frac{3}{4}\right).\left(1-\frac{3}{7}\right).\left(1-\frac{3}{10}\right)........\left(1-\frac{3}{97}\right).\left(1-\frac{3}{100}\right)\)
\(=\frac{1}{4}.\frac{4}{7}.\frac{7}{10}.......\frac{94}{97}.\frac{97}{100}\)
\(=\frac{1}{100}\)
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:
\(\left(1-\dfrac{3}{4}\right).\left(1-\dfrac{3}{7}\right).\left(1-\dfrac{3}{10}\right).\left(1-\dfrac{3}{13}\right).....\left(1-\dfrac{3}{97}\right).\left(1-\dfrac{3}{100}\right)\)
\(=\dfrac{1}{4}.\dfrac{4}{7}.\dfrac{7}{10}.\dfrac{10}{13}.....\dfrac{94}{97}.\dfrac{97}{100}\)
\(=\dfrac{1.4.7.10.....94.97}{4.7.10.13.....97.100}\)
\(=\dfrac{1}{100}\)
Tính:
a)1*4*7+4*7*10+7*10*13+....+100*103*106
b)1*4+4*7+7*10+.....+100*103
c)1*1*1+4*4*4+7*7*7+....+99*99*99
d)1*3*3*3+3*5*5*5+5*7*7*7+.....+49*51*51*51
e)1*99+2*98+3*97+......+50*50
f)1*99+3*97+5*95+....+49*51
Giúp mình nhé!
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 !!!
Tính tổng:(1-3/4).(1-3/7).(1-3/10).(1-3/13)....(1-3/97).(1-3/100) ( thách ai làm đc bài nay nhanh và đúng nhất nha.Minh se tick cho day.)
= 1/4 . 4/7 . 7/10 . 7/13 . ...... . 94/97 . 97/100
= 1/100
nhớ tk nha
Kết quả của dãy tính sau bằng cách nhanh nhất :
( 1 - 3/4 ) x ( 1 - 3/7 ) x ( 1 - 3/10 ) x ( 1 - 3/13 ) x ......x ( 1 - 3/97 ) x ( 1 - 3/100 )
( 1 - 3/4 ) x ( 1 - 3/7 ) x ( 1 - 3/10 ) x ( 1 - 3/13 ) x ......x ( 1 - 3/97 ) x ( 1 - 3/100 ) .
= 1/4 x 4/7 x 7/10 x ... x 97/100 .
Khử đi các số giống nhau .
= 1/100 nha bạn .
1 − 4 3 1 − 7 3 1 − (10 3 ... 1 − 97 3 1 − 100 3 = 4 1 . 7 4 . 10 7 ..... 97 94 . 100 97 = 4.7.10.....97.100 1.4.7.....94.97 = 100 1