nhanh đi bà con hàng xóm

nhanh đi bớ người ta

Đặt A = 1/3 + 2/3² + 3/3³ + 4/3^4 + ... + 100/3^100

=> 3A= 1 + 2/3 + 3/3² + 4/3³ + .... + 100/3^99

=> 3A-A = 1 + (2/3 - 1/3) + (3/3² - 2/3²) +...+ (100/3^99 - 99/3^99) - 100/3^100

=> 2A= 1+ 1/3 + 1/3² + 1/3³ +...+ 1/3^99 - 100/3^100

Đặt B = 1/3 + 1/3² + 1/3³ +...+ 1/3^99

=> 3B = 1 + 1/3 + 1/3² + 1/3³ +...+ 1/3^98

=> 2B = 1 - 1/3^99 => B = (1 - 1/3^99)/2

Thay vào 2A => 2A= 1+ 1/2 - 1/(2x3^99) - 100/3^100 < 1+ 1/2 = 3/2

=> A < 3/4

- 4 . 5 + ( - 4 ) . 2 + ( - 4 ) . 3 = - 4 . ( 5 + 2 + 3 ) = - 4 . 10 = -40

= -4 x ( 5 + 2 + 3 )

= -4 x 10

= -40

-4x5+-4x2+-4x3

=-4x(5+2+3)

=-4x10

=-40

1)

3*(x+1)-12=15                        4*(x-3)+12=40

=> 3*(x+1)=27                       => 4*(x-3)=28

=> x+1=9                              => x-3=7

=> x=8                                  => x=10

tui nhầm ở câu cuối đó 6 * 19 * 4 + 3 * 81* 8

mình nhầm câu cuối 6*19*4+3*81*8

\(53.39+47.39-53.21+47.21\)

\(=39.\left(53-39\right)-\left(53-47\right).21\)

\(=39.14-6.21\)

\(=39.7.2-6.2.7\)

\(=7.2.\left(39-6\right)\)

\(=14.33\)

Bạn Sai rùi ! mk k nhầm nha

\(53.39+47.39-53.21-47.21\)

\(=\left(39-21\right).53+47.\left(39-21\right)\)

\(=\left(39-21\right).\left(53+47\right)\)

\(=18.100=1800\)

Nhầm:D@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

\(\left(3\dfrac{1}{2}-x\right).1\dfrac{1}{4}=-1\dfrac{1}{20}\)

\(\left(\dfrac{7}{2}-x\right).\dfrac{5}{4}=-\dfrac{21}{20}\)

\(\dfrac{7}{2}-x=-\dfrac{21}{20}:\dfrac{5}{4}\)

\(\dfrac{7}{2}-x=-\dfrac{21}{25}\)

\(x=\dfrac{7}{2}-\left(-\dfrac{21}{25}\right)\)

\(x=\dfrac{217}{50}\)

Vậy \(x=\dfrac{217}{50}\)\(\)

\(\left(3\dfrac{1}{2}-x\right).1\dfrac{1}{4}=-1\dfrac{1}{20}\)

\(\left(\dfrac{7}{2}-x\right).\dfrac{5}{4}=-\dfrac{21}{20}\)

\(\left(\dfrac{7}{2}-x\right)=-\dfrac{21}{25}\)

\(x=\dfrac{217}{50}\)

\(\left(3\dfrac{1}{2}-x\right).1\dfrac{1}{4}=-1\dfrac{1}{20}\)

\(\left(\dfrac{7}{2}-x\right).\dfrac{5}{4}=\dfrac{-21}{20}\)

\(\left(\dfrac{7}{2}-x\right)=\dfrac{-21}{20}:\dfrac{5}{4}\)

\(\dfrac{7}{2}-x=\dfrac{-21}{20}.\dfrac{4}{5}\)

\(\dfrac{7}{2}-x=\dfrac{\left(-21\right).4}{20.5}\)

\(\dfrac{7}{2}-x=\dfrac{\left(-21\right).1}{5.5}\)

\(\dfrac{7}{2}-x=\dfrac{-21}{25}\)

\(x=\dfrac{7}{2}-\dfrac{-21}{25}\)

\(x=\dfrac{175}{50}+\dfrac{42}{50}\)

\(x=\dfrac{217}{50}\)

a. [ -2/3 + 3/7 ] : 4/5 + [ -1/3 + 4/7 ]  : 4/5 = 0

b. 5/9 : [ 1/11 - 5/22 ] + 5/9 : [ 1/15 - 2/3 ] = -5

HT/nhớ k cho tôi nha

Ai làm xong sớm nhất tui k cho

nntttgfgfgt

số cam sau lần bán thứ hai là:(24+3/4):3/3=33 quả

số cam còn lại sau lần bán thứ nhất là: (33+1/3):2/3=50 quả

vậy số cam bác nông dân mang đi bán là: (50+1/2):1/2=1001 quả

đ/s:1001 quả

cho tui nha!!!!! ai cho tui tui cầu cho may mắn cả năm,học hành đạt thàh tích xuất sắc ;)))))

\(\text{A= 1/2 + 1/3 + 1/4 + 1/5 + 1/6 + 1/7 + 1/8 +...+1/99+1/100}\)

\(A=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{99}-\dfrac{1}{100}\)

\(A=1-\dfrac{1}{100}=\dfrac{99}{100}\)

bằng 99/100

tíck cho mik nha

3/4 + 2 =2 3/4

1/5 x 3 3/4=3/4

11/4 - 2 =3/4

1/5 : 3 3/4=4/75

TK nha