b) A=(X-1,75):0,01

<=>41,25=(X-1,75):0,01

<=> X-1,75=0,4125

<=> X=2,1625

A=(1-0,75).80.X

<=>41,25=0,25.80.X

<=>X=2,0625

Học tốt

\(B=\left(1-\dfrac{1}{2}\right)\left(1-\dfrac{1}{3}\right)\left(1-\dfrac{1}{4}\right)...\left(1-\dfrac{1}{2004}\right)\)

\(B=\dfrac{1}{2}\cdot\dfrac{2}{3}\cdot\dfrac{3}{4}\cdot...\cdot\dfrac{2003}{2004}\)

\(B=\dfrac{1\cdot2\cdot3\cdot...\cdot2003}{2\cdot3\cdot4\cdot...\cdot2004}\)

\(B=\dfrac{1}{2004}\)

B=(1-1/2)x(1-1/3)x(1-1/4)x(1-1/5)...(1-1/2003)x(1-1/2004)

B=1/2x2/3x3/4x4/5x...x2002/2003x2003/2004

B=1/2004

A)\(a=3\frac{3}{4}\)

suy ra \(\frac{\left(3\frac{3}{4}-1,75\right):0,01}{\left(1-0,75\right)x80}\)

        = 10

b)     nếu A = 41,25 thì ta có \(\frac{\left(a-1,75\right):0,01}{\left(1-0,75\right)x80}=41,25\)

                               suy ra ( a -1,75) : 0,01: ( 1-0,75) x 80 = 41.25

                                         ( a - 1, 75 ) : 0,01 : 0,25 = 41,25 : 80

                                        ( a - 1, 75 ) : 0,01 : 0,25  = 33/64

                                         a - 1,75                         = 33 / 64 x 0,25 x 0,01

                                         a - 1,75                         = 33/25600

                                        a                                    = 33/ 25600+ 1,75

                                       a                                     = 1,751289063 

          = 

b) Ta có: 

\(A=\frac{\left(a-1,75\right)\div0,01}{\left(1-0,75\right)\times80}=41,25\)

\(\frac{\left(a-1,75\right)\div0,01}{0,25\times80}=41,25\)

\(\left(a-1,75\right)\div0,01\div20=41,25\)

\(\left(a-1,75\right)\div0,01=41,25\times20\)

\(\left(a-1,75\right)\div0,01=825\)

\(\left(a-1,75\right)=825\times0,01\)

\(a-1,75=8,25\)

 \(a=8,25+1,75\)

\(a=10\)

Vậy a phải bằng 10 thì biểu thức A có giá trị là 41,25 

L = 1/2 x 2/3 x 3/4 x ... X 2003/2004.rút gọn biểu thứ ta được 1/2004.

từng cách một nhé bạn

Bài 2:

\(B=\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right).......\left(1-\frac{1}{2004}\right)\)

\(=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}....\frac{2003}{2004}\)

\(=\frac{1}{2004}\)

Bài 2

=1/2 x 2/3 ... x 2003/2004

=1/2004

1. Tính giá trị biểu thức:

a) (2/5 x 25/29) + (3/5 x 25/29)
= (50/145) + (75/145)
= 125/145

b) (5/2 x 3/7) - (3/14 : 6/7)
= 15/14 - (3/14 x 7/6)
= 15/14 - 1/2
= (30/28) - (14/28)
= 16/28
= 4/7

c) (15/4 : 5/12) - (6/5 : 11/15)
= (15/4 x 12/5) - (6/5 x 15/11)
= 180/20 - 90/55
= 9 - 18/11
= (99/11) - (18/11)
= 81/11
= 7 4/11

2. Tính giá trị biểu thức:

a) (2/3) + (20/21 x 3/2 x 7/5)
= 2/3 + (60/210)
= 2/3 + 2/7
= (14/21) + (6/21)
= 20/21

b) (5/17 x 21/32 x 47/24 x 0)
= 0

c) (11/3 x 26/7) - (26/7 x 8/3)
= (286/21) - (208/21)
= 78/21
= 3 9/21
= 3 3/7

3. Tìm x:

a) (25/8) : x = 5/16
=> (25/8) x (16/5) = x
=> 4 = x

b) x + (7/15) = 6/15
=> x = (6/15) - (7/15)
=> x = -1/15

c) x : (28/49) = 7/12
=> x x (49/28) = 7/12
=> x = (7/12) x (28/49)
=> x = 1/2

4. Tìm x:

a) 6 x x = (5/8) : (3/4)
=> 6x = (5/8) x (4/3)
=> 6x = 20/24
=> 6x = 5/6
=> x = (5/6) / 6
=> x = 5/36

câu,b,không,đủ,thông,tin,nhan,bạn.

\(B=\left(1-\frac{1}{3}\right)\left(1-\frac{1}{4}\right)\left(1-\frac{1}{5}\right)\cdot....\cdot\left(1-\frac{1}{2003}\right)\left(1-\frac{1}{2004}\right)\)

\(=\frac{2}{3}\cdot\frac{3}{4}\cdot\frac{4}{5}\cdot....\cdot\frac{2002}{2003}\cdot\frac{2003}{2004}\)

\(=\frac{2\cdot3\cdot4\cdot...\cdot2002\cdot2003}{3\cdot4\cdot5\cdot...\cdot2003\cdot2004}=\frac{1}{1002}\)