bn l-ike cho mk trước đã

Ta có : A=20/11×13 + 20/13×15 +20/15×17+...+20/53×55

A = 10 ×( 2/11×13+2/13×15+...12/53×55)

A = 10 ×(1/11-1/13+1/13-1/15+1/15-1/17+...+1/53-1/55)

A = 10 × (1/11-1/55)

A =10 × 4/55

A = 8/11

a. Đ

b. S

c. Đ

d. S

x : 2 = 70

x = 70 x 2

x = 140

a) => (x+32) - 17 = 42:2 = 21

=> x+32 = 21+17 = 38

=> x=38-32=6

b) => 61+(53-x) = 1785:17=105

=> 53-x = 105-61=44

=> x = 53-44 =9

c) => x^2 +54 -32 = 244:2 = 122

=> x^2 +22 = 122

=> x^2 = 122-2=100

=> x= 10 hoặc -10

giải oy pn **** giùm mk nka

a. X = 6

b. X = 9

c. X = 10

a)[(x+32)+17] :2=42

(x+32)+17=42.2

(x+32)+17=84

x+32=84-17

x+32=67

x=67-32

x=35

b)[61+(53-x)]:17=1785

61+(53-x)=1785.17

61+(53-x)=10345

53-x=30345-61

53-x=30284

x=53-30284

x=-30231

47 x 83 + 21 x 53 + 47 x 17 - 79 x 53

= 47 x (83 + 17) + 53 x (21 - 79)

= 47 x 100 + 53 x (-58)

= 4700 - 3074

= 1626

Chưa học số âm

\(47.83+21.53+47.17-79.53\)

\(=47.\left(83+17\right)+53.\left(79+21\right)\)

\(=47.100+53.100\)

\(=4700+5300\)

\(=10000\)

x + 21/40 = 53/40

x = 53/40 - 21/40

x = 32/40 = 4/5

34/35 : x = 17/5

x = 34/35 : 17/5

x = 2/7

`x + 3 / 4 xx 7 / 10 = 53 / 40`

`x + 21 / 40 = 53 / 40`

`x = 53 / 40 - 21 / 40`

`x = 32 / 40`

`x = 4 / 5`

____________________________

`( 2 / 5 + 4 / 7 ) : x = 17 / 5`

`( 14 / 35 + 20 / 35 ) : x = 17 / 5`

`34 / 35 : x = 17 / 5`

`x = 34 / 35 : 17 / 5`

`x = 34 / 35 xx 5 / 17`

`x = 2 / 7`