\(A\)\(=\)\(2x\)\(+\)\(3y\)\(+\)\(9x\)\(+\)\(8y\)

\(A\)\(=\)\(\left(2x+9x\right)\)\(+\)\(\left(3y+8y\right)\)

\(A\)\(=\)        \(11x\)       \(+\)      \(11y\)

\(x+y=10\)\(\Rightarrow\)\(A\)\(=\)\(11\)\(.\)\(10\)\(=\)\(110\)

 \(A=2x+3y+9x+8y\)

\(A=\left(2x+9x\right)+\left(3y+8y\right)\)

\(A=11x+11y\)

\(\Rightarrow A=11.\left(x+y\right)\)

mà x+y =10 nên

\(A=11.10=110\)

a=110

Tính nhanh :

a)8 x 45 + 55 x 8 

= 8x(45+55)

= 8x100

=800

28 x 69 + 31 x 28 

= 28x(69+31)

= 28x100

=2800

Ta có :

8 x 45 + 55 x 8 

= 8 x ( 45 + 55 )

= 8 x 100 

= 800

28 x 69 + 31 x 28 

= 28 x ( 69 + 31 )

= 28 x 100 

= 2800

mik tl trước mak 

Bài 6:

a)\(\left(-18\right)-\left(-3\right)-12\)

\(=\left(-18\right)+3-12\)

\(=-15-12\)

\(=-27\)

b)\(85.\left(35-27\right)-35.\left(85-27\right)\)

\(=85.35-85.27-35.85+35.27\)

\(=85.\left(35-27-35\right)+35.27\)

\(=85.\left(-27\right)+35.27\)

\(=27.\left(-85+35\right)\)

\(=27.\left(-50\right)\)

\(=-1350\)

c)\(\left(-45\right).69+31.\left(-45\right)\)

\(=\left(-45\right).\left(69+31\right)\)

\(=\left(-45\right).100\)

\(=-4500\)

Bài 7:

a)\(\left(2-x\right)+10=-14\)

\(\Rightarrow2-x=-24\)

\(\Rightarrow x=26\)

b)\(14.\left|x\right|=28\)

\(\Rightarrow\left|x\right|=2\)

\(\Rightarrow\orbr{\begin{cases}x=2\\x=-2\end{cases}}\)

c)\(31-\left(17+x\right)=55\)

\(\Rightarrow17+x=-24\)

\(\Rightarrow x=-41\)

(-18)-(-3)-12=-27

85.(35-27)-35.(85-27)=-1350

(-45).69+31.(-45)=-4500

(2-x)+10=-14

\(\Leftrightarrow\)(2-x)=-14-10

\(\Leftrightarrow\)2-x=-24

\(\Rightarrow\)x=2-(-24)

\(\Rightarrow\)x=26

14.lxl=28

\(\Leftrightarrow\)lxl=28:14

\(\Leftrightarrow\)lxl=2

\(\Rightarrow\)x=-2

-69.|-45|-31.|45|

-69.45-31.45

45.(-69-31)

45.-100

-4500

=-4500

-69 . |-45| - 31 . |45|.

= -69 . 45 - 31 . 45

= [ (-69) - 31 ] . 45

= (-100) . 45

= -4500.

#Học tốt.

-69. | -45 | - 31 . | 45|

= -69 . 45 - 31 . 45

= 45 ( -69 - 31)

= 45. (-100)

= -4500

hok tốt!

-69 x |-45| -31.| 45|

= -69.45 - 31.45

= 45(-69 - 31)

= 45.(-100)

= -4500

    -69 x |-45| - 31 x |45|

= -69 x 45 - 31 x 45

= 45 x (-69 -31)

= 45 x (-100)

= -4500

~Đúng nhớ tk giúp mình nhé!! Thanks 😘

#Học_tốt

(-69)x|-45|-31x|45|

=(-69)x45-31x45

=45x[(-69)-31]

=45x(-100)

=-4500

\(\left(-69\right)\times\left|-45\right|-31\times\left|45\right|\)

\(=\left(-69\right)\times45-31\times45\)

\(=45\left(-69-31\right)\)

\(=45\times100\)

\(=4500\)

Bài 6: Thực hiện phép tính

a)(-18)-(-3)-12

= (-18) + 3 - 12

= (-15) - 12

= - 3

b)85.(35-27)-35.(85-27)

= 85. 8 - 35. 58

= 680. 2030

= 1380400

c)(-45).69+31.(-45)

= (-45) . (69 + 31)

= (-45) . 100

= - 4500

Bài 7:Tìm x thuộc Z, biết:

a)(2-x)+10=-14

2-x = 14 - 10

2-x = 4

x = 2 - 4

x = - 2

b)14.|x|=28

|x| = 28 : 14

|x| = 2

⇒ x ϵ {2;-2}

a) ( 735 - 135 ) + ( 243 - 143 ) = 600 + 100 

= 700

b) 31 x ( 118 - 48 ) = 31 x 70 

= 2170

c) ( 25 x 32 ) x7 = 800 x 7

= 2400

d ) 47 x ( 63 + 47 ) - 38

= 47 x 100 - 38

= 4700 - 38 

=4662

h ) ( 53 + 47 ) x ( 39 + 21 ) = 100 x 60 

= 6000