x - 99/5 + x - 99/15 + x - 99/25 + x - 99/35 = 0
tìm x
Tính nhẩm
46 x 99 34 x 11 25 x 12 15 x 4 45 x 6 13 x 99 16 x 19 35 x 98
125 x 16 47 x 101
\(46\cdot99\)
\(=46\cdot\left(100-1\right)\)
\(=46\cdot100-46\)
\(=4600-46\)
\(=4554\)
___________
\(34\cdot11\)
\(=34\cdot\left(10+1\right)\)
\(=34\cdot10+34\)
\(=340+34\)
\(=374\)
___________
\(25\cdot12\)
\(=5\cdot5\cdot12\)
\(=5\cdot60\)
\(=300\)
__________
\(15\cdot4\)
\(=15\cdot2\cdot2\)
\(=30\cdot2\)
\(=60\)
____________
\(45\cdot6\)
\(=45\cdot2\cdot3\)
\(=90\cdot3\)
\(=2700\)
________
\(13\cdot99\)
\(=13\cdot\left(100-1\right)\)
\(=13\cdot100-13\)
\(=1300-13\)
\(=1287\)
______________
\(16\cdot19\)
\(=16\cdot\left(20-1\right)\)
\(=16\cdot20-16\)
\(=320-16\)
\(=304\)
_____________
\(35\cdot98\)
\(=35\cdot\left(100-2\right)\)
\(=35\cdot100-35\cdot2\)
\(=3500-70\)
\(=3430\)
____________
\(125\cdot16\)
\(=125\cdot8\cdot2\)
\(=1000\cdot2\)
\(=2000\)
___________
\(47\cdot101\)
\(=47\cdot\left(100+1\right)\)
\(=47\cdot100+47\)
\(=4700+47\)
\(=4747\)
46 x 99 =4554 , 34 x 11 = 374 , 25 x 12 =- 300 , 15 x 4 = 60 , 45 x 6 = 270 , 13 x 99 = 1287 , 16 x 19 = 304
35 x 98 = 3430 , 125 x 16 = 2000 , 47 x 101 = 4747
x/3 + x/15 +x/35+...+x/99 = 2023 x 5/11
\(\dfrac{x}{3}+\dfrac{x}{15}+\dfrac{x}{35}+...+\dfrac{x}{99}=2023\times\dfrac{5}{11}\)
\(\dfrac{x}{1.3}+\dfrac{x}{3.5}+\dfrac{x}{5.7}+...+\dfrac{x}{9.11}=2023\times\dfrac{5}{11}\)
\(x-\dfrac{x}{3}+\dfrac{x}{3}-\dfrac{x}{5}+\dfrac{x}{5}-\dfrac{x}{7}+...+\dfrac{x}{9}-\dfrac{x}{11}=2023\times\dfrac{5}{11}\)
\(x-\dfrac{x}{11}=2023\times\dfrac{5}{11}\)
\(\dfrac{11\times x-x}{11}=2023\times\dfrac{5}{11}\)
\(\dfrac{10\times x}{11}=2023\times\dfrac{5}{11}\)
\(\dfrac{10}{11}\times x=2023\times\dfrac{5}{11}\)
\(x=2023\times\dfrac{5}{11}:\dfrac{10}{11}\)
\(x=\dfrac{2023}{2}=1011,5\)
#AvoidMe
Tính nhanh
8/9 x 15/16 x 24/25 x 35/36 x ... x 99/100
= (8x15x24x35x...x99) / (9x16x25x36x...x100)
= (4x2x5x3x6x2x2x5x7x...x9x11) / (9x4x2x2x5x5x6x3x2x...x25x4)
= 11/(4x25)
= 11/100
Mình không chắc lắm
a ) A = 1/3 + 1/15 + 1/35 + 1/63 + 1/99 + 1/143
b) x + ( x + 1 ) + ( x + 2 ) + ....+ ( x + 99 ) = 14950
éc ô éc
a) \(A=\dfrac{1}{3}+\dfrac{1}{5}+\dfrac{1}{35}+\dfrac{1}{63}+\dfrac{1}{99}+\dfrac{1}{143}\)
\(A=\dfrac{1}{1.3}+\dfrac{1}{3.5}+\dfrac{1}{5.7}+\dfrac{1}{7.9}+\dfrac{1}{9.10}+\dfrac{1}{143}\)
\(A=\dfrac{1}{2}.\left(1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{10}\right)+\dfrac{1}{143}\)
\(A=\dfrac{1}{2}.\left(1-\dfrac{1}{100}\right)+\dfrac{1}{143}=\dfrac{1}{2}.\dfrac{99}{100}+\dfrac{1}{143}=\dfrac{99}{200}+\dfrac{1}{143}=\dfrac{99.143+200.1}{200.143}=\dfrac{14157+200}{28600}=\dfrac{14357}{28600}\)
b) \(x+\left(x+1\right)+\left(x+2\right)+...+\left(x+99\right)=14950\)
\(\Rightarrow x+x+...+x+\left(1+2+...+99\right)=14950\)
\(\Rightarrow100x+\left(\left(99+1\right):2\right).99:2=14950\)
\(\Rightarrow100x+2475=14950\Rightarrow100x=12475\Rightarrow x=\dfrac{12475}{100}=\dfrac{499}{4}\)
các bn ơi giúp mk với mai mk đi hc rùi
47 . ( 23 + 50 ) -23 . ( 47 + 50 )
(- 33 ) . ( - 5 ) - 33 . 4 + 33
25 . 99 + | -25 | . 99 -99 . ( -37 ) + | -13 | . 99
bài tìm x
2 . ( x - 5 ) = -12
x mũ 3 -1 =26
2 . ( x -5 ) - 3 . ( x + 7 ) =14
-7 . ( 5 - x ) - 2 . ( x - 10 ) = 15
8 . ( x - | -7 | ) - 6 . ( x- 2 ) = | -8 | . 6 - 50
12 . ( x - 4 ) + 6 . ( x- 2 ) - 16 . ( x+ 3 ) = 7 . | - 4 |
47. (23 + 50)- 23. ( 47+50 )
= 47. 23+ 47. 50- 23. 47 - 23. 50
=47. 50 - 23. 50
= 50 .( 47 -23)
=50. 24 = 1200
(-33 ). (-5) - 33 . 4 + 33
= 33 ( 5 - 4 + 1)
=33 . 2 = 66
giup minh voi
3 | + | 3 | + … + | 3 | = | |
1 x 4 | 4 x 7 | 262 x 265 |
|
2/15 + 2/35 + 2/63 +2/99 + .......2/23 x 25 + 2/675
\(\frac{2}{15}+\frac{2}{35}+\frac{2}{63}+....+\frac{2}{575}+\frac{2}{675}\)
\(=\frac{2}{3\times5}+\frac{2}{5\times7}+\frac{2}{7\times9}+...+\frac{2}{23\times25}+\frac{2}{25\times27}\)
\(=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{23}-\frac{1}{25}+\frac{1}{25}-\frac{1}{27}\)
\(=\frac{1}{3}-\frac{1}{27}=\frac{8}{27}\)
Vậy ....
\(\frac{2}{15}+\frac{2}{35}+\frac{2}{69}+........+\frac{2}{575}+\frac{2}{675}\)
\(=\frac{2}{3\times5}+\frac{2}{5\times7}+........+\frac{2}{23\times25}+\frac{2}{25\times27}\)
\(=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+.......+\frac{1}{23}-\frac{1}{25}+\frac{1}{25}-\frac{1}{27}\)
\(=\frac{1}{3}-\frac{1}{27}\)
\(=\frac{8}{27}\)
\(\frac{2}{15}+\frac{2}{35}+\frac{2}{63}+\frac{2}{99}+...+\frac{2}{575}+\frac{2}{675}\)
\(=\frac{2}{3\times5}+\frac{2}{5\times7}+\frac{2}{7\times9}+\frac{2}{9\times11}+...+\frac{2}{23\times25}+\frac{2}{25\times27}\)
\(=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+...+\frac{1}{23}-\frac{1}{25}+\frac{1}{25}-\frac{1}{27}\)
\(=\frac{1}{3}-\frac{1}{27}\)
\(=\frac{8}{27}\)
_Chúc bạn học tốt_
x+5/3+x+5/15+x+5/35+x+5/65+x+5/99=20/11
giúp mk giải nhanh bài này nha
Tính nhanh
a,(1+2 +3 +...+99) x (13 x 15 – 12 x 15 –15)
b,2+4+ 6+...+ 98+100–(1+3 +5 +...+97+99)
a)
Ta có : ( 1 + 2 + 3 + ... + 99)
Số số hạng là: ( 99 - 1 ) : 1 + 1 = 100
Tổng là: ( 99 + 1 ) x 100 : 2 = 5000
=> 5000 x ( 13 - 12 - 1 ) x 15
=> 5000 x 10 x 15
=> 50000 x 15
=> 750000
Ko muốn vt nx :))
1/3 x 1/8 x 1/15 x 1/24 x 1/35 x ... x 1/99
=1/(1x3)x1/(2x4)x...x1/(9x11)
=1/(1x3x2x4x...x9x11)
=1/(1x2x3x3x4x4x5x5x...x9x10x11)