1a) -54 . 76 + 12 .(-76) + 76.(-34)

= (-54 - 12 - 34).76

= -100 . 76

= -176

b) 37.(63 - 24) - 63.(24 + 37)

= 37 . 63 - 37 . 24 - 63.24 - 63 . 37

= (37.63 - 63.37) - (37 + 63) . 24

= 0 - 100 . 24

= - 2400

2a) x + (-27) = -23 - x

=> x + x = -23 + 27

=> 2x = 4

=> x = 4 : 2

=> x = 2

b) xy + 2x - y = 15

=> x(y + 2) - y = 15

=> x(y + 2) - (y + 2) = 13

=> (x - 1)(y + 2) = 13 = 1 . 13 = 13 . 1

Lập bảng :

Vậy ...

\(A=\frac{34}{7.13}+\frac{51}{13.22}+\frac{85}{22.37}+\frac{68}{37.49}\)

\(=\frac{17.2}{7.13}+\frac{17.3}{13.22}+\frac{17.5}{22.37}+\frac{17.4}{37.49}\)

\(=17\left(\frac{2}{7.13}+\frac{3}{13.22}+\frac{5}{22.37}+\frac{4}{37.49}\right)\)

\(=\frac{17}{3}\left(\frac{6}{7.13}+\frac{9}{13.22}+\frac{15}{22.37}+\frac{12}{37.49}\right)\)

\(=\frac{17}{3}\left(\frac{1}{7}-\frac{1}{13}+\frac{1}{13}-\frac{1}{22}+...+\frac{1}{37}-\frac{1}{49}\right)\)

\(=\frac{17}{3}\left(\frac{1}{7}-\frac{1}{49}\right)\)\(=\frac{17}{3}.\frac{6}{49}=\frac{17.2}{49}=\frac{34}{49}\)

Có : \(\frac{17}{24}=\frac{34}{48}\)

Vì 48 < 49 => \(\frac{34}{48}>\frac{34}{49}\). Hay \(\frac{17}{24}>A\)

cảm ơn Văn B ? nha !

(-37) x 86+37 x 76

= 37 x (-86) + 37 x 76

= 37 x [(-86) + 76]

= 37 x (-10)

= -370

37 . 24 + 37 . 76 + 63 .79 + 63 . 21

= 37 . ( 24 + 76 ) + 63 . ( 79 + 21 )

= 37 . 100 + 63 . 100

= ( 37 + 63 ) . 100

= 100 . 100

= 10000

e, 37 . 24 + 37 . 76 + 63 .79 + 63 . 21

 = 37 . ( 24 + 76 ) + 63 . ( 79 + 21 )

= 37 . 100 + 63 . 100

= 100 . ( 37 + 63 )

= 100 . 100

= 100²

Tính bằng cách hợp lý nhất:

\(a)\)\(-64.159+136.\left(-8\right)^2+123.64\)

\(=64.\left(-159\right)+136.64+123.64\)

\(=64.\left(-159+123+136\right)\)

\(=64.100\)

\(=6400\)

\(b)\)\(84.\left(16-37\right)-16.\left(37+84\right)\)

\(=84.16-84.37-16.37-16.84\)

\(=84.\left(16-16\right)-37.\left(84+16\right)\)

\(=84.0-37.100\)

\(=0-3700\)

\(=-3700\)

1

37.(43-51)-43.(37-51)

=37.43-37.51-43.37-43.51

=(37.43-43.57)-(37.51-43.51)

=0-(-306)

=306

2

a.(x-1).(2x+2)=0

=>x-1 hoặc 2x+2=0

=>x=1 hoặc 2x=-2

=>x=1 hoặc x=-1

Vậy x=+1

b.(6x-12).(x-3)=0

=>6x-12 hoặc x-3=0

=>6x=12 hoặc x=3

=>x=2 hoặc x=3

Vậy x=2 hoặc x=3

Ai đúng mình like !