a) - ( -25) - ( 202 + 125 ) + 402 = 100

b) - (-22) - ( 150 + 22 ) - 50 = (-200)

c) ( - 505 ) - (- 154 + 495 ) - ( - 846 ) = 990

d) ( 35 - 814 ) - ( 186 - 65 ) = (-1030)

`#040911`

`7x = 154`

`\Rightarrow x = 154 \div 7`

`\Rightarrow x = 22`

Vậy, `x = 22.`

X=154:7

x=22

Ta có : 7x + 32 : 8 = 154 + 2x 

=> 7x + 4 = 154 + 2x

=> 7x - 2x = 154 - 4

=> 5x = 150

=> x = 30

7x - 2x = 154 - 4 <=> 5x = 150 => x = 30

=

=

h)x² + 7x-30=6+7x

không phải trừ nha

xy - 7x + y = -22

=> x(y - 7) + y - 7 = -29

=> x(y - 7) + (y - 7) = -29

=> (x+1)(y - 7) = -29

ta có bảng :

\(xy-7x+y=-22\)

\(xy+y-7x=-22\)

\(y\left(x+1\right)-7x=-22\)

\(y\left(x+1\right)-7x-7=-22-7\)

\(y\left(x+1\right)-\left(7x+7\right)=-29\)

\(y\left(x+1\right)-7.\left(x+1\right)=-29\)

\(\left(y-7\right)-\left(x+1\right)=-29\)

Ta có bảng sau:

Vậy ....................................

\(Q=\dfrac{-2015}{2016}\cdot\left(-50\right)\cdot\dfrac{-153}{154}\cdot1\dfrac{1}{2015}\cdot20\%\)

\(=\dfrac{-2015}{2016}\cdot\left(-50\right)\cdot\dfrac{-153}{154}\cdot\dfrac{2016}{2015}\cdot\dfrac{1}{5}\\ =\left(-\dfrac{2015}{2016}\cdot\dfrac{2016}{2015}\right)\cdot\left(-50\cdot\dfrac{1}{5}\right)\cdot-\dfrac{153}{154}\\ =\left(-1\right)\cdot\left(-10\right)\cdot\left(-\dfrac{153}{154}\right)\\ =10\cdot\left(-\dfrac{153}{154}\right)\\ =-\dfrac{1530}{154}\\ =-\dfrac{765}{77}\)

a) 

<=> 720 : [ 41 - ( 7x^2 - 5 ) ] = 40

<=>         41 - ( 7x^2 - 5 )      = 720 : 40

<=>         41 - ( 7x^2 - 5 )      = 18

<=>                  7x^2 - 5         = 41 - 18

<=>                  7x^2 - 5         = 23

<=>                 7x^2               = 23 + 5

<=>                 7x^2               = 28

<=>                  x^2                = 28 : 7

<=>                  x^2                = 4

<=>                  x^2                = 2^2

<=>                  x                   = 2

b) 10: 1/10

   40: 1/40

   88: 1/88

   154: 1/154

   238: 1/238

Rồi b tách mẫu số ra như sau:

\(\frac{1}{10}+\frac{1}{40}+\frac{1}{88}+\frac{1}{154}+\frac{1}{238}\)

=> \(\frac{1}{2\times5}+\frac{1}{5\times8}+\frac{1}{8\times11}+\frac{1}{11\times14}+\frac{1}{14\times17}\)

Đó rồi tính tiếp nha

a, 41-(7x^2-5)=720:40=18

7x^2-5=41-18=23

7x^2=23+5=28

x^2=28:7=4

x= 2 và -2

b, luôn bằng 0 có tính chất