K
Khách

Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.

4 tháng 12 2018

3 phần hay 1 phần đấy

4 tháng 12 2018

435 + ( - 43 ) + ( - 487 ) + ( - 57 ) + 383 + ( - 415 )

= 435 + ( - 415 ) + ( - 43 ) + 383 + ( - 487 ) + ( - 57 )

= [ 435 + ( - 415 ) ] + [ ( - 43 ) + 383 ] + [ ( - 487 ) + ( - 57 ) ] 

= 20 + 340 + ( - 544 )

= 360 + ( - 544 )

= - 184

1316 + 317 + ( - 1213 ) + ( - 314 + ( - 85 ) )

= [ 1316 + ( - 1213 ) ] + [ 317 + ( - 314 + ( - 85 ) ) ]

= 103 + ( - 82 )

= 21

1 + ( - 4 ) + 7 + ( - 10 ) + 13 + ( - 16 )   

= [ 1 + ( - 10 ) ] + [ ( - 4 ) + ( - 16 ) ] + [ 7 + 13 ]

= ( - 9 ) + ( - 20 ) + 20

= ( - 9 ) + [ ( - 20 ) + 20 ]

= ( - 9 ) + 0 

= - 9 

28 tháng 12 2016

a) \(56+\left(-29\right)+\left(-7\right)+28+13+\left(-35\right)\)

\(=27+\left(-7\right)+28+13+\left(-35\right)\)

\(=20+28+13+\left(-35\right)\)

\(=48+13+\left(-35\right)\)

\(=61+\left(-35\right)\)

\(=26\)

b) \(\left(-213\right)+186+\left(-14\right)+217+54+\left(-49\right)\)

\(=\left(-27\right)+\left(-14\right)+217+54+\left(-49\right)\)

\(=\left(-41\right)+217+54+\left(-49\right)\)

\(=176+54+\left(-49\right)\)

\(=230+\left(-49\right)\)

\(=181\)

c) \(435+\left(-43\right)+\left(-483\right)+\left(-57\right)+383+\left(-415\right)\)

\(=392+\left(-483\right)+\left(-57\right)+383+\left(-415\right)\)

\(=\left(-91\right)+\left(-57\right)+383+\left(-415\right)\)

\(=\left(-148\right)+383+\left(-415\right)\)

\(=235+\left(-415\right)\)

\(=-180\)

26 tháng 9 2019

Phương Văn Cảnh giúp mk bài này vskhocroi

26 tháng 9 2019

Vế trái: 4/(x+2).(x+6)+7/(x+6).(x+13)

<=>1/x+2 -1/x+6 +1/x+6 -1/x+13

<=>1/x+2-1/x+13

=> 1/x+2-1/x+13=2x+1/(x+2).(x+16) -3/(x+13).(x+16)

<=>1/x+2 - 1/x+13 + 1/x+13 - 1/x+16=2x+1/(x+2).(x+16)

<=>1/x+2 - 1/x+16=2x+1/(x+2).(x+16)

<=> 14/(x+2).(x+16)= 2x+1/(x+2).(x+16)

<=> 2x+1=14

<=> 2x=14-1

<=> 2x=13

<=> x=13:2

<=> x=13/2

Vậy x=13/2

Chúc bạn học tốt

20 tháng 9 2020

A) \(\frac{7}{\left(x+3\right)\left(x+10\right)}+\frac{11}{\left(x+10\right)\left(x+21\right)}+\frac{13}{\left(x+21\right)\left(x+34\right)}\)

\(=\frac{\left(x+10\right)-\left(x+3\right)}{\left(x+3\right)\left(x+10\right)}+\frac{\left(x+21\right)-\left(x+10\right)}{\left(x+10\right)\left(x+21\right)}+\frac{\left(x+34\right)-\left(x+21\right)}{\left(x+21\right)\left(x+34\right)}\)

\(=\frac{1}{x+3}-\frac{1}{x+10}+\frac{1}{x+10}-\frac{1}{x+21}+\frac{1}{x+21}-\frac{1}{x+34}\)

\(=\frac{1}{x+3}-\frac{1}{x+34}\)

\(=\frac{\left(x+34\right)-\left(x+3\right)}{\left(x+3\right)\left(x+34\right)}\)\(=\frac{x}{\left(x+3\right)\left(x+34\right)}\)

\(\Rightarrow\left(x+34\right)-\left(x+3\right)=x\)

\(\Rightarrow x=31\)

Vậy, x = 31 

20 tháng 9 2020

Bạn áp dụng: \(\frac{k}{x\cdot\left(x+k\right)}=\frac{1}{x}-\frac{1}{x+k}\) với    \(x,k\inℝ;x\ne0;x\ne-k\)

Chứng minh: \(\frac{1}{x}-\frac{1}{x+k}=\frac{x+k}{x\left(x+k\right)}-\frac{x}{x\left(x+k\right)}=\frac{x+k-x}{x\left(x+k\right)}=\frac{k}{x\left(x+k\right)}\)

b: Ta có: \(\left(x+2\right)\left(x+3\right)\left(x+4\right)\left(x+5\right)-24=0\)

\(\Leftrightarrow\left(x^2+7x+10\right)\left(x^2+7x+12\right)-24=0\)

\(\Leftrightarrow\left(x^2+7x\right)^2+22\left(x^2+7x\right)+120-24=0\)

\(\Leftrightarrow x^2+7x+6=0\)

\(\Leftrightarrow\left(x+1\right)\left(x+6\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-1\\x=-6\end{matrix}\right.\)

\(\Leftrightarrow\dfrac{3}{\left(x+1\right)\left(x+4\right)}+\dfrac{3}{\left(x+4\right)\left(x+7\right)}+\dfrac{3}{\left(x+7\right)\left(x+10\right)}+\dfrac{3}{\left(x+10\right)\left(x+13\right)}=\dfrac{12}{13}\)

\(\Leftrightarrow\dfrac{1}{x+1}-\dfrac{1}{x+13}=\dfrac{12}{13}\)

\(\Leftrightarrow12\left(x+1\right)\left(x+13\right)=13\left(x+13\right)-13\left(x+1\right)=156\)

\(\Leftrightarrow\left(x+1\right)\left(x+13\right)=13\)

\(\Leftrightarrow x^2+14x=0\)

=>x=0 hoặc x=-14