a) 42 x 43 + 42 x 56 + 42 = 42 x (43 + 56 + 1) = 42 x 100 = 4200

b) 48 x 8 + 42 x 8 + 8 x 10 = 8 x (48 + 42 + 10) = 8 x 100 = 800

a) 42 x 43 + 42 x 56 + 42

= 42 x 43 + 42 x 56 + 42 x 1

= 42 x ( 43 + 56 + 1 )

= 42 x (     99     + 1 )

= 42 x            100

=          4200

b) 48 x 8 + 42 x 8 + 8 x10

= 8 x ( 48 + 42 + 10 )

= 8 x (     90     + 10 )

= 8 x          100

=      800

a) 42 x 43 + 42 x 56 + 42

= 42 x 43 + 42 x 56 + 42 x 1

= 42 x ( 56 + 43 + 1 )

= 42 x 100 

= 4200

b) 48 x 8 + 42 x 8 + 8 x 10 

= 8 x ( 48 + 42 + 10 )

= 8 x 100

= 800

k mk nha

\(x\) + (-31) - (42) = -45

\(x\) - (31 + 42) = -45

\(x\) - 73 = -45

\(x\)       = -45 + 73

\(x\)      = 28

305 - \(x\) + 14  = 48 + (\(x\) - 23)

(305  + 14) - \(x\) = (48 - 23) + \(x\)

319 - \(x\)           = 25 + \(x\) 

\(x\) + \(x\)              = 319 - 25

2\(x\)                  = 294

   \(x\)                 = 294 : 2

   \(x\)                 = 147

\(x-43=\left(35-x\right)\) - 48

\(x\) - 43 = 35 - \(x\) - 48

\(x\) - 43 = - (48 - 35) - \(x\)

\(x\) - 43  = - 13 - \(x\)

\(x\) + \(x\)    = -13 + 43

2\(x\)         = 30

  \(x\)         = 30 : 2

  \(x\)         = 15

x + (-31) - 42 = -45

x - 73 = -45

x = -45 + 73

x = 28

-------

305 - x + 14 = 48 + (x - 23)

319 - x = 48 + x - 23

-x - x = 25 - 319

-2x = -294

x = -294 : (-2)

x = 147

--------

x - 43 = (35 - x) - 48

x = 35 - x - 48 + 43

x + x = 30

2x = 30

x = 30 : 2

x = 15

$x$ + (-31) - (42) = -45

$x$ - (31 + 42) = -45

$x$ - 73 = -45

$x$       = -45 + 73

$x$      = 28

305 - $x$ + 14  = 48 + ($x$ - 23)

(305  + 14) - $x$ = (48 - 23) + $x$

319 - $x$           = 25 + $x$ 

$x$ + $x$              = 319 - 25

2$x$                  = 294

   $x$                 = 294 : 2

   $x$                 = 147

$x-43=\left(35-x\right)$ - 48

$x$ - 43 = 35 - $x$ - 48

$x$ - 43 = - (48 - 35) - $x$

$x$ - 43  = - 13 - $x$

$x$ + $x$    = -13 + 43

2$x$         = 30

  $x$         = 30 : 2

  $x$         = 15

1) \(x^2+x-6=x\left(x-2\right)+3\left(x-2\right)=\left(x+3\right)\left(x-2\right)\)

2) \(x^2-x-6=\left(x-3\right)\left(x+2\right)\)

3) \(x^2+2x-48=\left(x-6\right)\left(x+8\right)\)

4) \(x^2-2x-48=\left(x-8\right)\left(x+6\right)\)

5) \(x^2+x-42=\left(x-6\right)\left(x+7\right)\)

6) \(x^2-x-42=\left(x-7\right)\left(x+6\right).\)

bài này tìm x hay tìm cực trị vậy

1) \(x^2+x-6\)

\(=x^2-2x+3x-6\)

\(=\left(x^2-2x\right)+\left(3x-6\right)\)

\(=x\left(x-2\right)+3\left(x-2\right)\)

\(=\left(x-2\right)\left(x+3\right)\)

2) \(x^2-x-6\)

\(=x^2+2x-3x-6\)

\(=\left(x^2+2x\right)-\left(3x+6\right)\)

\(=x\left(x+2\right)-3\left(x+2\right)\)

\(=\left(x+2\right)\left(x-3\right)\)

3) \(x^2+2x-48\)

\(=x^2+8x-6x-48\)

\(=\left(x^2+8x\right)-\left(6x+48\right)\)

\(=x\left(x+8\right)-6\left(x+8\right)\)

\(=\left(x+8\right)\left(x-6\right)\)

4) \(x^2-2x-48\)

\(=x^2-8x+6x-48\)

\(=\left(x^2-8x\right)+\left(6x-48\right)\)

​\(=x\left(x-8\right)+6\left(x-8\right)\)​

\(=\left(x-8\right)\left(x+6\right)\)

5) \(x^2+x-42\)

\(=x^2+7x-6x-42\)

\(=\left(x^2+7x\right)-\left(6x+42\right)\)

\(=x\left(x+7\right)-6\left(x+7\right)\)

\(=\left(x+7\right)\left(x-6\right)\)

6) \(x^2-x-42\)

\(=x^2-7x+6x-42\)

\(=\left(x^2-7x\right)+\left(6x-42\right)\)

\(=x\left(x-7\right)+6\left(x-7\right)\)

\(=\left(x-7\right)\left(x+6\right)\)

(42 \(\times\)x - 48) : x = 30

42 \(\times\)x : x - 48 : x = 30

42 - 48 : x = 30

48 : x = 42 - 30

48 : x = 12

x = 48 : 12

x = 4

đúng không đây

đáp án đúng là 4

chuk học giỏi

x + 5 / 48 = 7 / 42

=> ( x + 5 ).42 = 48.7

=> x + 5 = ( 48.7 ) : 42

=> x + 5 = 336 : 42

=> x + 5 = 8

=> x = 8 - 5

=> x = 3

Vậy x = 3

x + 5/48 = 7/42

x = 7/42 - 5/48

x = 1/16

x+5/48=7/42

x=7/42-5/48

x=1/16

x + 5/48= 7/42

x           =  7/42 - 5/48

x           = 1/16

x+1/48=7/42

        x=7/42-1/48

        x=7/48

x+1/48 = 7/42

=> x= \(\frac{7}{42}-\frac{1}{48}=\frac{7}{48}\)

duyệt đi

sai đề 

bằng 6132 

42 x 50 + 84 x 48 = 6132 

nha bn 

chúc bn học giỏi nha

=6123 k mik nha làm ơn