a: =-231-16+75+25-9

=-240+100-16

=-140-16=-156

b: =231-17-77=231-94=137

d: =a+b+c-c-b+a=2a

\(A=\frac{7}{10.11}+\frac{7}{11.12}+\frac{7}{12.13}+...+\frac{7}{69.70}\)

\(A=7\left(\frac{1}{10.11}+\frac{1}{11.12}+\frac{1}{12.13}+....+\frac{1}{69.70}\right)\)

\(A=7\left(\frac{1}{10}-\frac{1}{11}+\frac{1}{11}-\frac{1}{12}+....+\frac{1}{69}-\frac{1}{70}\right)\)

\(A=7\left(\frac{1}{10}-\frac{1}{70}\right)\)

\(A=7\cdot\frac{3}{35}=\frac{21}{35}\)

\(A=\frac{7}{10\cdot11}+\frac{7}{11\cdot12}+\frac{7}{12\cdot13}+...+\frac{7}{69\cdot70}\)

\(A=7\left(\frac{1}{10\cdot11}+\frac{1}{11\cdot12}+\frac{1}{12\cdot13}+...+\frac{1}{69\cdot70}\right)\)

\(A=7\left(\frac{1}{10}-\frac{1}{11}+\frac{1}{11}-\frac{1}{12}+...+\frac{1}{69}-\frac{1}{70}\right)\)

\(A=7\left(\frac{1}{10}-\frac{1}{70}\right)=7\cdot\frac{3}{35}=\frac{3}{5}\)

\(B=\frac{1}{25\cdot27}+\frac{1}{27\cdot29}+\frac{1}{29\cdot31}+...+\frac{1}{73\cdot75}\)

\(B=\frac{1}{2}\left(\frac{2}{25\cdot27}+\frac{2}{27\cdot29}+\frac{2}{29\cdot31}+...+\frac{2}{73\cdot75}\right)\)

\(B=\frac{1}{2}\left(\frac{1}{25}-\frac{1}{27}+\frac{1}{27}-\frac{1}{29}+...+\frac{1}{73}-\frac{1}{75}\right)\)

\(B=\frac{1}{2}\left(\frac{1}{25}-\frac{1}{75}\right)=\frac{1}{2}\cdot\frac{2}{75}=\frac{1}{75}\)

\(C=\frac{4}{2\cdot4}+\frac{4}{4\cdot6}+\frac{4}{6\cdot8}+...+\frac{4}{2008\cdot2010}\)

\(C=\frac{4}{2}\left(\frac{2}{2\cdot4}+\frac{2}{4\cdot6}+\frac{2}{6\cdot8}+...+\frac{2}{2008\cdot2010}\right)\)

\(C=2\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+...+\frac{1}{2008}-\frac{1}{2010}\right)\)

\(C=2\left(\frac{1}{2}-\frac{1}{2010}\right)=2\cdot\frac{502}{1005}=\frac{1004}{1005}\)

\(B=\frac{1}{25.27}+\frac{1}{27.29}+\frac{1}{29.31}+...+\frac{1}{73.75}\)

\(2B=\frac{2}{25.27}+\frac{2}{27.29}+\frac{1}{29.31}+...+\frac{1}{73.75}\)

\(2B=\frac{1}{25}-\frac{1}{27}+\frac{1}{27}-\frac{1}{29}+...+\frac{1}{73}-\frac{1}{75}\)

\(2B=\frac{1}{25}-\frac{1}{75}=\frac{2}{75}\)

Ta thấy \(BCNN\left(-15;-25;-75\right)=-75\)

Do đó mẫu số chung của 3 phân số là -75

Khi đó \(\frac{7}{-15}=\frac{7.5}{-15.5}=\frac{35}{-75}\)

\(-\frac{8}{25}=\frac{-8.3}{-25.3}=\frac{-24}{-75}\)

\(75\left(-\frac{4}{25}+7\frac{1}{15}-5\frac{7}{75}\right)\)

\(=75\left(-\frac{4}{25}+\frac{106}{15}-\frac{382}{75}\right)\)

\(=75\left(-\frac{12}{75}+\frac{530}{75}-\frac{382}{75}\right)\)( ta thấy 75 là B( 25,15 ) nên 75 sẽ là mẫu số chung )

\(=75\left(\frac{518}{75}-\frac{382}{75}\right)\)

\(=75.\frac{136}{75}\)

\(=136\)

\(75\left(\frac{-4}{25}+7\frac{1}{15}-5\frac{7}{75}\right)=75\left(\frac{-12}{75}+\frac{530}{75}-\frac{382}{75}\right)\)

\(\frac{75.136}{75}=136\)

Đáp án là : 73,8666666                                                                                                                                                                                   Viết đúng cách là  : 73,866...

C =[125.(73-75)]:(-25)2

=125.(-2):(-25).2

=-250:(-50)

=5

E=125.9.(-4).(-8).25.7

=125.(-8).25.(-4).7.9

=-1000.(-100).63

=6300000

C = ( 125 . 73 - 125 . 75 ) : ( -50)

C = 125 .( -2 ) : (-50)

C = -250 : -50

C =  50

G = ( -3 )²+( -5)³: l -5 l

G = 9 + ( -125) : 5

G = 9 + ( -25 )

G= ( -16 )

E = 125 .9.*( -4 ) . ( -8) .25.7

E = 25.5 .( -4 ) .9 .2. ( -4 ) .25 .7

E =( -100 ).10.( -100).63

E = 10000.630

E = 630000

**** mha

\(=\dfrac{2}{3}+\dfrac{81}{25}+\dfrac{8}{7}=\dfrac{38}{21}+\dfrac{81}{25}=\dfrac{2651}{525}\)

=2651/525

mình còn ko bt cơ mà mai nộp r

mik chỉ lm đc 1 câu thôi mong bn like cho
(13911:3849−5211:3849):(4938.511)={(13+911).4938−(5+211).4938}:(4938.511)=4938.(13−5+911−211):(4938.511)=4938.(8+711):(4938.511)=(8+711):511=19

a) -7/25 . 11/13 + -7/25 . 2/13 - 18/25=-1

b) 5/7 . 1/3 - 5/7 . 1/4 - 5/7 . 1/12=0

c) 5 + 2/5 . 4+ 2/7 + 5 + 5/7 . 5+ 2/5=18

d) 75% - 3/2 + 0,5 - [ -1/2]^2=-1/2

a) -7/25 x 11/13 + -7/25 x 2/13 - 18/25 = -1

b) 5/7 x 1/3 - 5/7 x 1/4 - 5/7 x 1/12=0

c) 5 + 2/5 x 4+ 2/7 + 5 + 5/7 x 5+ 2/5=15.85714285

d) 75% - 3/2 + 0,5 - [ -1/2]^2=1/2

refer:

                                =2/3+81/25+8/7       =38/21+81/25 =  2651/525

`35/75 : 19/25 + 81/25 + 4.2/7`

=`38/75 xx 25/18 + 81/25 + 8/7`

=` 2/3 + 81/25 + 8/7`

= `293/75 + 8/7`

= `2651/525`