a: Ta có: \(142-\left[50-\left(2^3\cdot10-2^3\cdot5\right)\right]\)

\(=142-\left[50-80+40\right]\)

=142-10

=132

a. 142 - [50-(2³.10-2³.5)]

= 142 - [ 50 - ( 8 . 10 - 8 . 5 )]

= 142 - [ 50 - ( 80 - 40 )]

= 142 - [ 50 - 40 ]

= 142 - 10 = 132

b. 375 : { 32[ 4+(5.3² - 42 )]} - 14

= 375 : { 32[4+(5.9 - 42 )]} - 14

= 375 : { 32[4 + ( 45 - 42 )]} - 14

= 375 : {32[4+3]} - 14

= 375 : 224 - 14

c.{210 : [ 16+3.(6+3.2^2)]} - 3

= {210 : [ 16 + 3.(6+3.4)]} - 3

= { 210 :[16+3.(6+12)]}-3

= {210 : [ 16+3.18)]} - 3

= { 210 : [ 16 + 54]} - 3

= { 210 : 70 } - 3

= 30 - 3 = 27

d.500-{5.[409-(2^3 . 3-21^2)] - 1724}

= 500-{5.[409-(8 . 63 - 21^2] - 1724}

= 500 - { 5.[409- (504 -  441) - 1724}

= 500 -{ 5.[ 409 - 63 ] - 1724}

= 500 - { 5.346 - 1724}

= 500 - { 1720 - 1724 }

= 500 - 6 

= 494

a) 

\(x\cdot\left(x-4\right)=0\) 

\(\orbr{\begin{cases}x=0\\x-4=0\end{cases}}\)  

\(\orbr{\begin{cases}x=0\\x=0+4\end{cases}}\)

\(\orbr{\begin{cases}x=0\\x=4\end{cases}}\) 

b) 

\(375-\left(28+5x\right)=277\) 

\(28+5x=375-277\)  

\(28+5x=98\) 

\(5x=98-28\) 

\(5x=70\) 

\(x=14\) 

c) 

\(2x+24=46\) 

\(2x=46-24\) 

\(2x=22\) 

\(x=11\)

a) \(x\left(x-4\right)=0\Leftrightarrow\orbr{\begin{cases}x=0\\x=4\end{cases}}\)

b) \(375-\left(28+5x\right)=277\)

\(\Leftrightarrow5x=70\)

\(\Rightarrow x=14\)

c) \(5x-3x+24=46\)

\(\Leftrightarrow2x=22\)

\(\Rightarrow x=11\)

                                                     Bài giải

\(a,\text{ }x\left(x-4\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x=0\\x-4=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=0\\x=4\end{cases}}\)

\(\Rightarrow\text{ }x\in\left\{0\text{ ; }4\right\}\)

\(b,\text{ }375-\left(28+5x\right)=277\)

\(28+5x=375-277=98\)

\(5x=98-28=70\)

\(x=14\)

\(c,\text{ }5x-3x+24=46\)

\(2x+24=46\)

\(2x=22\)

\(x=11\)

mk biết có mỗi cách thôi, làm xằng vậy =))

Ta có :

\(5x=3y\)

\(\Leftrightarrow\dfrac{x}{3}=\dfrac{y}{5}\)

Đặt :

\(\dfrac{x}{3}=\dfrac{y}{5}=k\) \(\Leftrightarrow\left\{{}\begin{matrix}x=3k\\y=5k\end{matrix}\right.\)\(\left(1\right)\)

Thay \(\left(1\right)\) vào \(xy=375\) ta có :

\(3k.5k=375\)

\(\Leftrightarrow15k^2=375\)

\(\Leftrightarrow\left[{}\begin{matrix}k=25\\k=-25\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}k=5\\k=-5\end{matrix}\right.\)

+) \(k=5\Leftrightarrow\left[{}\begin{matrix}x=3.5=15\\y=5.5=25\end{matrix}\right.\)

+) \(k=-5\Leftrightarrow\left[{}\begin{matrix}x=3.\left(-5\right)=-15\\y=5\left(-5\right)=-25\end{matrix}\right.\)

Vậy ..

1 Cách nhé

\(5x=3y\Leftrightarrow\dfrac{x}{3}=\dfrac{y}{5}\)

Đặt : \(\dfrac{x}{3}=\dfrac{y}{5}=k\)

Ta có : \(\dfrac{x}{3}=k\Leftrightarrow x=3k\)

\(\dfrac{y}{5}=k\Leftrightarrow y=5k\)

Mà : \(3k.5k=375\)

\(\Leftrightarrow15k^2=375\)

\(\Leftrightarrow k^2=25\)

\(\Leftrightarrow\left[{}\begin{matrix}k=5\\k=-5\end{matrix}\right.\)

Khi \(k=5\), thì : \(\left\{{}\begin{matrix}x=15\\y=25\end{matrix}\right.\)

Khi \(k=-5,\) thì : \(\left\{{}\begin{matrix}x=-15\\y=-25\end{matrix}\right.\)

Vậy ..........

Giải:

Ta có: \(5x=3y\)

\(\Leftrightarrow\dfrac{x}{3}=\dfrac{y}{5}\)

Đặt \(\dfrac{x}{3}=\dfrac{y}{5}=k\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=3k\\y=5k\end{matrix}\right.\)

Mà \(xy=375\)

\(\Leftrightarrow3k.5k=375\)

\(\Leftrightarrow15k^2=375\)

\(\Leftrightarrow k^2=\dfrac{375}{15}=25\)

\(\Leftrightarrow\left[{}\begin{matrix}k=5\\k=-5\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=3.5\\x=3.\left(-5\right)\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=15\\x=-15\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}y=5.5\\x=5.\left(-5\right)\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=25\\x=-25\end{matrix}\right.\)

Vậy ...

Chúc bạn học tốt!

a, X+86=144                                                                        b, 5x X =375

            X=144-86                                                                           X=375:5

           X= 58                                                                                   X=75

a, X+86=144                                                            b, 5x X=375

         X=144-86                                                                   X=375:5

          X=58                                                                          X=75

a> ta có : X + 86 = 114

                 X = 114 - 86

                X = 28

b > 5 × X = 375

             X = 375 : 5 

            X = 75

# chúc bạn học tốt ạ #

\(\left(5x-1\right)^2+2\left(1-5x\right)\left(4+5x\right)+\left(5x+4\right)^2\)

\(=\left(5x-1\right)^2-2\left(5x-1\right)\left(5x+4\right)+\left(5x+4\right)^2\)

\(=\left[\left(5x-1\right)-\left(5x+4\right)\right]^2\)

\(=\left(5x-1-5x-4\right)^2\)

\(=\left(-5\right)^2\)

\(=25\)

a) ( 2x - 25 ) : 3 = 27

     ( 2x - 25 )     = 81

       2x               = 81 + 25

       2x               = 106

         x               = 53

b) ( x - 3 ) ( 8 - x ) = 0

\(\Rightarrow\orbr{\begin{cases}x-3=0\\8-x=0\end{cases}}\)\(\Rightarrow\orbr{\begin{cases}x=3\\x=8\end{cases}}\)

d) 516 - ( 246 + 3x ) = 26 

                246 + 3x   = 490

                           3x  = 244

                             x  = 

a)(2x - 25) : 3 = 27

=> 2x - 25 = 27 . 3

=> 2x - 25 = 81

=> 2x = 81 + 25 = 106

=> x = 106 : 2 = 53

b)(x - 3).(8 - x) = 0

=> x - 3 = 0 hoặc 8 - x = 0

=> x = 3 hoặc x = 8

c) 889 - 5x - 2x = 375

=>889 - 7x = 375

=>7x = 889 - 375

=>7x = 514 

=>x = 514/7

d) 516 - ( 246 + 3x ) = 26

=> 246 + 3x = 516 - 26

=> 246 + 3x = 490

=> 3x = 490 - 246

=> 3x = 244

=> x = 244/3

e) x + 1 + 2 + 3 + ... + 50 = 1500

=>x + (1 + 2 + 3 + ... + 50) = 1500

=>x + 50.(50+1):2 = 1500

=>x + 1275 = 1500

=>x = 1500 - 1275

=>x = 225

Tìm số tự nhiên x thỏa mãn  : 

a , ( 2x - 25 ) : 3 = 27 

2x - 25 = 27 × 3 

2x - 25 = 81 

2x = 81 + 25 

2x = 106 

x = 106 : 2 

x = 53 

Vậy x = 53 

b, ( x - 3 ) . ( 8 - x ) = 0 

<=> x - 3 = 0 hoặc 8 - x = 0

<=> x = 0 + 3 hoặc x = 8 - 0 

<=> x = 3 hoặc x = 8

Vậy x € { 3 ; 8 } 

  A = (5\(x\) + 1)² + (5\(x\) - 1)² - 2.( 5\(x\) +1).(5\(x\) - 1) tại \(x\) = 1

Thay \(x\) = 1 vào A ta có:

A = (5.1 + 1)² + (5.1 - 1)² - 2.(5.1 + 1).(5.1 - 1)

A = 6² + 4² - 2.6.4 

A = 36 + 16 - 48

A = 52 - 48

A = 4

\(5^x+5^{x+1}+5^{x+2}+5^{x+3}=1+2+3+...+87+88-4^2\)

=>\(5^x+5^x\cdot5+5^x\cdot25+5^x\cdot125=88\cdot\dfrac{\left(88+1\right)}{2}-16\)

=>\(156\cdot5^x=44\cdot89-16=3900\)

=>\(5^x=\dfrac{3900}{156}=25\)

=>x=2

cái cuối là mũ 2 nha

P = (5x − 1) + 2(1 − 5x)(4 + 5x) + (5x+4)\(^2\) 

   = 5x – 1 + (2 – 10x).( 4+ 5x) + (5x+4)\(^2\) 

   = 5x – 1 + 8 + 10x – 40x – 50x\(^2\) + 25x\(^2\) + 40x + 16

   = ( - 50x\(^2\) + 25x\(^2\) ) + ( 5x + 10x – 40x + 40x) + ( - 1+ 8 + 16 )

    = -25x\(^2\) + 15x + 23