a) x = -4.-11/2

x = 22

b) (15 - x ).5 = ( x + 9 ).3

75 - 5x = x3 + 27

8x = 48

x = 6

Chu vi của mảnh vườn hình chữ nhật đó là:

( 5,5 + 3,75 ) . 2 = 18,5 ( m )

Số khóm hoa cần trồng là:

18,5 : 1/4 = 74 ( khóm hoa )

Đáp số: 74 khóm hoa.

a) 1/5 + 4/5 : x = 0,75

1/5 + 4/5 : x = 3/4

4/5 : x = 3/4 - 1/5

4/5 : x = 11/20

x = 4/5 : 11/20

x = 16/11

Vậy x = 16/11

b) x + 1/2 = 1 - x

( x . 2 ) + 1/2 = 1

( x . 2 ) = 1 - 1/2

x . 2 = 1/2

x = 1/2 : 2

x = 1/4

Vậy x = 1/4

 

a) 2/3 . 5/4 - 3/4 . 2/3

= 2/3 . ( 5/4 - 3/4 )

= 2/3 . 1/2

= 2/6 = 1/3

b) 2 . ( -3/2 )^2 - 7/2

= 2 . ( -3/4 ) - 7/2

= 2 . ( -17/4 )

= -17/2

c) -3/4 . 5( 3/13 ) - 0,75 . 36/13

= -3/4 . 68/13 - 3/4 . 36/13

= 3/4 . ( -68/13 - 36/13 )

= 3/4 . ( -8 )

= -6

 

a) ( 1/2 + 1,5 ) . x = 1/5

2 . x = 1/5

x = 1/5 : 2 

x = 1/10

Vậy x = 1/10

b) [ -1(3/5) + x ] : 12/13 = 2(1/6)

( -8/5 + x ) = 13/6 . 12/13

( -8/5 + x ) = 2

x = 2 - (-8/5)

x = 18/5

Vậy x = 18/5

c) [ x : 2(1/3) ] . 1/7 = -3/8

( x : 7/3 ) = -3/8 : 1/7

( x : 7/3 ) = -21/8

x = -21/8 . 7/3

x = -49/8

Vậy x = -49/8

d) -4/7 . x + 7/5 = 1/8 : -1(2/3)

-4/7 . x + 7/5 = -3/40

-4/7 . x = -3/40 - 7/5

-4/7 . x = -59/40

x = -59/40 : -4/7

x = 413/160

Vậy x = 413/160

 

a) 1/2 - ( x + 1/3 ) = 5/6

x +1/3 = 1/2 - 5/6

x + 1/3 = -1/3

x = -1/3 - 1/3

x = -2/3

Vậy x = -2/3

b) ( 3/8 - 1/5 ) + ( 5/8 - x ) = 1/5

7/40 + ( 5/8 - x ) = 1/5

5/8 - x = 1/5 - 7/40

5/8 - x = 1/40

x = 5/8 - 1/40

x = 3/5

Vậy x = 3/5

a) -1,62 + 2/5 + x = 7

2/5 + x = 7 - ( -1,62 )

2/5 + x = 8,62

x = 8,62 - 2/5

x = 8,22

vậy x = 8,22

b) 4(2/5) - x = -1/5 + 1/2

23/5 - x = 3/10

x = 23/5 - 3/10

x = 43/10

Vậy x = 43/10

c) -4/7 - x = 3/5 - 2x

-x - 4/7 = -2x + 3/5

-x - 4/7 + 4/7 = -2x + 3/5 + 4/7

-x = -2x + 41/35

-x + 2x = -2x + 41/35 + 2x

x = 41/35

Vậy x = 41/35

d) 5/7 - 1/13 + 0,25 = 3(1/2) - x

5/7 - 1/13 + 1/4 = 7/2 - x

323/364 = 7/2 - x

x = 7/2 - 323/364

x = 951/364

Vậy x = 951/364

a) -1,62 + 2/5 + x = 7

2/5 + x = 7 - ( -1,62 )

2/5 + x = 8,62

x = 8,62 - 2/5

x = 8,22

vậy x = 8,22

b) 4(2/5) - x = -1/5 + 1/2

23/5 - x = 3/10

x = 23/5 - 3/10

x = 43/10

Vậy x = 43/10

c) -4/7 - x = 3/5 - 2x

-x - 4/7 = -2x + 3/5

-x - 4/7 + 4/7 = -2x + 3/5 + 4/7

-x = -2x + 41/35

-x + 2x = -2x + 41/35 + 2x

x = 41/35

Vậy x = 41/35

d) 5/7 - 1/13 + 0,25 = 3(1/2) - x

5/7 - 1/13 + 1/4 = 7/2 - x

323/364 = 7/2 - x

x = 7/2 - 323/364

x = 951/364

Vậy x = 951/364

a) -1,62 + 2/5 + x = 7

2/5 + x = 7 - ( -1,62 )

2/5 + x = 8,62

x = 8,62 - 2/5

x = 8,22

vậy x = 8,22

b) 4(2/5) - x = -1/5 + 1/2

23/5 - x = 3/10

x = 23/5 - 3/10

x = 43/10

Vậy x = 43/10

c) -4/7 - x = 3/5 - 2x

-x - 4/7 = -2x + 3/5

-x - 4/7 + 4/7 = -2x + 3/5 + 4/7

-x = -2x + 41/35

-x + 2x = -2x + 41/35 + 2x

x = 41/35

Vậy x = 41/35

d) 5/7 - 1/13 + 0,25 = 3(1/2) - x

5/7 - 1/13 + 1/4 = 7/2 - x

323/364 = 7/2 - x

x = 7/2 - 323/364

x = 951/364

Vậy x = 951/364

A = ( 2/7 . 1/4 - 1/3 . 2/7 ) : ( 2/7 . 3/9 - 2/7 . 2/5 )

A = 2/7 . [( 1/4 - 1/3 ) : ( 3/9 - 2/5 )]

A = 2/7 . [ -1/12 : -1/15 ]

A = 2/7 . 5/4

A = 5/14

B = ( 1/5 - 2/7 ) . 3/4 - 3/4 . ( 1/3 - 2/7 ) / 1/5 . 2/7 - 1/3 . ( 2/7 + 3/9 ) + 3/9 . 1/5

B = 3/4 - 3/4 / 3/9 + 3/9

B = 0 : 2/3 

B = 0