\(-12\left(7-72\right)-25\left(55-43\right)\)

\(=-12\cdot\left(-65\right)-25\cdot12\)

\(=12\cdot65-25\cdot12\)

\(=12\left(65-25\right)\)

\(=12\cdot40=480\)

=−12⋅(−65)−25⋅12

   (-12) x (7 - 72) - 25 x (55 - 43)

= -12 x (-65) - 25 x 12

= 12 x [-(-65) - 25]

= 12 x [65 - 25]

= 12 x 40

=  480 

TL:

\(\text{a) (-12).(7-72)-25.(55-43) = (-12).(-65)-25.12 = 12.(65-25) = 12.40 = 480 b) (39-19):(-2)+(34-22).5 = 20:(-2)+12.5 = -10+60 = 50}\)

HT

a) (-12).(7-72)-25.(55-43)

=(-12).(-65)-25.12

=12.(65-25)

=12.40

=480

b) (39-19):(-2)+(34-22).5

=20:(-2)+12.5

=-10+60

^HT^

ai làm hộ với

mk chỉ cần nhìn sơ qua là biết có câu dễ sao bn ko tự nghĩ đi hơi dễ rồi trừ khi bn đố tôi chục câu tiếng anh vật lí văn

\(2x+\frac{7}{6}+\frac{13}{12}+\frac{21}{20}+\frac{31}{30}+\frac{43}{42}+\frac{57}{56}+\frac{73}{72}+\frac{91}{90}=10\)
=> \(2x+\frac{6+1}{6}+\frac{12+1}{12}+....+\frac{90+1}{90}=10\)
=> \(2x+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{90}+10=10\)
=> \(2x+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{90}=0\)
=>\(2x+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{9.10}=0\)
=>\(2x+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}=0\)
=> \(2x-\frac{1}{10}=0\)
=>2x=\(\frac{1}{10}\)=> x=1/20
 

mình có bị nhầm chỗ dấu suy ra thứ 3. đáng lẽ ra biểu thức đó cộng 8 chứ k phải cộng 10 do mình sơ ý nên bạn hãy sủa lại chỗ ấy

\(2x+\dfrac{7}{6}+\dfrac{13}{12}+\dfrac{21}{20}+\dfrac{31}{30}+\dfrac{43}{42}+\dfrac{57}{56}+\dfrac{73}{72}+\dfrac{91}{90}=10\)

\(2x+\left(1+\dfrac{1}{6}\right)+\left(1+\dfrac{1}{12}\right)+\left(1+\dfrac{1}{20}\right)+\left(1+\dfrac{1}{30}\right)+\left(1+\dfrac{1}{42}\right)+\left(1+\dfrac{1}{56}\right)+\left(1+\dfrac{1}{72}\right)+\left(1+\dfrac{1}{90}\right)=10\)

\(2x+8+\left(\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}+\dfrac{1}{72}+\dfrac{1}{90}\right)=10\)

\(2x+8+\left(\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}+\dfrac{1}{5.6}+\dfrac{1}{6.7}+\dfrac{1}{7.8}+\dfrac{1}{8.9}+\dfrac{1}{9.10}\right)=10\)

\(2x+8+\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{10}\right)=10\)

\(2x+8+\left(\dfrac{1}{2}-\dfrac{1}{10}\right)=10\)

~ Chúc bạn học tốt ~

2x+\(\dfrac{7}{2.3}+\dfrac{13}{3.4}+\dfrac{21}{4.5}+...+\dfrac{91}{9.10}=10\)

\(2x+7\left(\dfrac{1}{2.3}\right)+13\left(\dfrac{1}{3.4}\right)+...+91\left(\dfrac{1}{9.10}\right)=10\)

\(2x+\left(7+13+...+91\right)\left(\dfrac{1}{2.3}+\dfrac{1}{3.4}+...+\dfrac{1}{9.10}\right)=10\)

\(2x+336+\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{9}-\dfrac{1}{10}\right)=10\)

\(2x+336+\left(\dfrac{1}{2}-\dfrac{1}{10}\right)=10\)

\(2x+336.\dfrac{2}{5}=10\)

\(2x+\dfrac{672}{5}=10\)

\(2x=10-\dfrac{672}{5}\)

\(2x=-\dfrac{622}{5}\)

\(x=-\dfrac{311}{5}\)

Tick nha 0o0^^^Nhi^^^0o0

trả hay 

a) (-12). (7 - 72) - 25. (55 - 43) 

= (-12). (- 65) - 25. 12 

= 12. 65 – 12. 25

= 12. (65 - 25) 

= 12. 40 

= 480

b) (39 - 19) : (- 2) + (34 - 22). 5 

= 20 : (- 2) + 12. 5 

= - 10 + 60

= 60 - 10 

= 50.