\(71\frac{38}{45}-\left(43\frac{8}{45}-1\frac{17}{57}\right)\)

\(=71\frac{38}{45}-43\frac{8}{45}+1\frac{17}{57}\)

\(=\frac{86}{3}+\frac{74}{57}\)

\(=\frac{1708}{57}\)

Hc tốt #

sai me roi

=71+38/45- 43+8/45 +1+17/57

=(71 \(\frac{38}{45}-43\frac{8}{45}\))+ 1+17/57=28+2/3+1+17/57=29+55/57=29/55/57

1670/57

1670/57

a)(37-17).(-5)+23.(-6).(-8)

=20.(-5)+23.[(-6).(-8)]

=-100+23.(-48)

=-100+(-1104)

=-1004

b)(-57).(67-34)-67.(34-57)

=(-57).33-67.(-23)

=(-1881)-(-1541)

=-340

vi ca hai ko co uoc chung vi thê UCLN la1

\(A=\frac{3}{2}-\frac{5}{6}+\frac{13}{12}-\frac{19}{20}+\frac{31}{30}-\frac{41}{42}+\frac{57}{56}-\frac{71}{72}+\frac{91}{90}-\frac{109}{110}\)

\(\Rightarrow A=\left(1+\frac{1}{2}\right)-\left(1-\frac{1}{6}\right)+\cdot\cdot\cdot+\left(1+\frac{1}{90}\right)-\left(1-\frac{1}{110}\right)\)

\(\Rightarrow A=1+\frac{1}{2}-1+\frac{1}{6}+\cdot\cdot\cdot+1+\frac{1}{90}-1+\frac{1}{110}\)

\(\Rightarrow A=\left[\left(1-1\right)+\frac{1}{2}+\frac{1}{6}\right]+\cdot\cdot\cdot+\left[\left(1-1\right)+\frac{1}{90}+\frac{1}{110}\right]\)

\(\Rightarrow A=\frac{1}{2}+\frac{1}{6}+\cdot\cdot\cdot+\frac{1}{90}+\frac{1}{110}\)

\(\Rightarrow A=\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\cdot\cdot\cdot+\frac{1}{9\cdot10}+\frac{1}{10\cdot11}\)

\(\Rightarrow A=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\cdot\cdot\cdot+\frac{1}{10}-\frac{1}{11}\)

\(\Rightarrow A=1-\frac{1}{11}\)

\(\Rightarrow A=\frac{10}{11}\)

(51.39 + 51.18) : 57
= 51.(39+18) :57
= 51.57 :57

=51.1

=51

Sách Giáo Khoa

a) (37 - 17).(-5) + 23.(-13 - 17)
 = 20.(-5) + 23.(-30)
 = (-100) + (-690)
 = -790

b) (-57).(67 - 34) - 67.(34 - 57)
 = (-57).33 - 67.(-23)
 = -1881 + 1541
 = -340
   
hoặc:
   (-57).(67 - 34) - 67.(34 - 57)
 = (-57).67 – (-57).34 – 67.34 + 67.57
 = [67.(-57) + 67.57] – [(-57).34 + 67.34]
 = 67(-57 + 57) - 34(-57 + 67)
 = 67.0 - 34.10
 = 0 - 

a) (37 - 17).(-5) + 23.(-13 - 17)

= 20.(-5) + 23.(-30)

= (-100) + (-690) = -790

b) (-57).(67 - 34) - 67.(34 - 57)

= (-57).33 - 67.(-23)

= -1881 + 1541

= -340

hoặc: (-57).(67 - 34) - 67.(34 - 57)

= (-57).67 – (-57).34 – 67.34 + 67.57

= [67.(-57) + 67.57] – [(-57).34 + 67.34]

= 67(-57 + 57) - 34(-57 + 67)

= 67.0 - 34.10

= 0 - 340

= -340

\(2^{x+3}.4^2=64\Leftrightarrow2^{x+3}.2^4=64\Leftrightarrow2^{x+7}=2^6\Leftrightarrow x+7=6\Leftrightarrow x=-1\)