tự làm đi

\(460+85\times4=\left(x+200\right)\times4\)

\(\left(x+200\right)\times4=460+340\)

\(\left(x+200\right)\times4=800\)

\(x+200=800:4\)

\(x+200=200\)

\(x=200-200\)

\(x=0\)

~~~

\(\left(x-7\right)\left(2x-8\right)=0\)

\(+, TH1: x - 7 = 0\)

\(x=0+7\)

\(x=7\)

\(+, TH2 : 2x - 8 = 0 \)

\(2x=0+8\)

\(2x=8\)

\(x=8:2\)

\(x=4\)

~~~

\(x-280:35=5\times54\)

\(x-8=270\)

\(x=270+8\)

\(x=278\)

~~~

\(324+16\times\left(2x+3\right)=404\)

\(16\times\left(2x+3\right)=404-324\)

\(16\times\left(2x+3\right)=80\)

\(2x+3=80:16\)

\(2x+3=5\)

\(2x=5-3\)

\(2x=2\)

\(x=2:2\)

\(x=1\)

#\(Toru\)

`460 + 85 xx 4 = ( x + 200) xx 4`

`460 + 340 = (x+200)xx4`

` 800= (x+200)xx4`

`x+200=800:4`

`x+200=200`

`x=200-200`

`x=0`

__

`(x-7)(2x-8)=0`

`@ TH1`

`x-7=0`

`x=0+7`

`x=7`

`@ TH2`

`2x-8=0`

`2x=0+8`

`2x=8`

`x=8:2`

`x=4`

__

`x -280 : 35=5xx54`

`x -280 : 35=270`

`x-8=270`

`x=270+8`

`x=278`

__

`324 + 16xx(2x+3)=404`

`16xx(2x+3)=404 -324`

`16xx(2x+3)=80`

`2x+3=80:16`

`2x+3=5`

`2x=5-3`

`2x=2`

`x=2:2`

`x=1`

1. A

2. B

3. A

4. B

1.    444 x 5 = 222 x 2 x 5 = 222 x 10 = 2220
2.    282 x 5 = 280 + 2 x 5 = 280 x 10 = 2800
3.    4 x 8 x 7 x 25 = (8 x 7) x (25 x4) = 56 x 100 = 5600
4.    25 x 8 x 9 = (25 x 4) x (4 x 9) = 100 x 36 = 3600
a.Đúng         b.Sai

1. sai

2. Sai

3. đúng

4.sai

dài quá ko làm nha!!!

a)9.x + 1=73

 9x=73-1

9x=72

  x=72:9

  x=8

b)2.x - 5 = -17 - 12

2x-5=-29

2x=-29+5

2x=-24

  x=-24:2

  x=-12

c)10 - x - 5 = - 5 - 7 -11

10-x-5=-12-11

10-x-5=-23

 10-x=-23+5 

  10-x=18

       x=10-18

       x=-8

d)(-9) . x + 3 = (-2) . (-7) +16

-9x+3=14+16

-9x+3=30

-9x=30-3

-9x=27

   x=27:(-9)

   x=-3

(-12) . x - 34 =2

-12x=2+34

-12x=36

     x=36:(-12)

     x=-3

(-11).x + 9 =130

-11x=130-9

-11x=121

     x=121:(-11)

     x=11 

(-5) .x + 5 = (-15) .(-4) -12

-5x+5=60-12

-5x+5=48

-5x=48-5

-5x=43

   x=43:(-5)

  x=-8,6

IxI -3=0

|x|=3

=>x=+3

(7 - IxI).(2.x - 4) =0

*7-|x|=0            * 2x-4=0

|x|=7                   2x=4

=>x=+7                 x=4:2

                             x=2

280-(x-140):35 =270

(x-140):35=280-270

(x-140):35=10

x-140=10.35

x-140=350

       x=350+140

       x=490

(1900 - 2.x ) : 35- 32 =16

1900-2x=(16+32).35

1900-2x=1680

         2x=1900-1680

         2x=220

           x=220:2

           x=110

720 :[41-(2x -5 )] =2³ .5

720:[41-(2x-5)]=40

41-(2x-5)=720:40

41-(2x-5)=18

2x-5=41-18

2x-5=23

2x=23+5

2x=28

  x=28:2

  x=14

(x - 5).(x² - 4 ) =0

* x-5=0           * x²-4=0

      x=0+5         x²=4

      x=5             x²=2²

                    => x=+2

Đặt \(\frac{x}{10}=\frac{y}{7}=k\Rightarrow x=10k;y=7k\)

Có: x.y=280

\(\Leftrightarrow10k\cdot7k=280\)

\(\Leftrightarrow70k^2=280\)

\(\Leftrightarrow k^2=4\Leftrightarrow\left[\begin{array}{nghiempt}k=2\\k=-2\end{array}\right.\)

Với k=2 thì x=20 ;y=14

Với k=-2 thì x=-20 ; y=-14

Theo t/c của dãy tỉ số bawng nhau ta có : 

\(\frac{x}{10}=\frac{y}{7}=\frac{xy}{10.7}=\frac{280}{70}=4\)

\(\frac{x}{10}=4\Rightarrow x=4.10=40\)

\(\frac{y}{7}=4\Rightarrow y=4.7=28\)

Vậy x = 40 y = 28 

Đặt : \(\frac{x}{10}=\frac{y}{7}=k\)

\(\Rightarrow\frac{x}{10}=k\Rightarrow x=10k\)

\(\Rightarrow\frac{y}{7}=k\Rightarrow y=7k\)

Ta có : \(10k.7k=280\)

            \(\Rightarrow70k^2=280\)

            \(\Rightarrow k^2=4\)

            \(\Rightarrow k=\pm2\)

Khi \(x=2\) , ta có :

  \(\frac{x}{10}=2\Rightarrow x=20\)

  \(\frac{y}{7}=2\Rightarrow y=2.7=14\)

Khi \(x=-2\) , ta có : 

  \(\frac{x}{10}=-2\Rightarrow x=-20\)

  \(\frac{y}{7}=-2\Rightarrow y=-14\)

Vậy .....................

Đặt : \(\frac{x}{10}=\frac{y}{7}=k\)

\(\Rightarrow\frac{x}{10}=k\)

\(\Rightarrow\frac{y}{7}=k\)

\(\Rightarrow x=10k;y=7k\)

Ta có : \(10k.7k=280\)

\(70k^2=280\)

\(k^2=4\)

\(\Leftrightarrow\orbr{\begin{cases}k=2\\k=-2\end{cases}}\)

TH1 : \(k=2\)

\(\frac{x}{10}=2\Rightarrow x=20\)

\(\frac{y}{7}=2\Rightarrow y=14\)

TH2 : \(k=-2\)

\(\frac{x}{10}=-2\Rightarrow x=-20\)

\(\frac{y}{7}=-2\Rightarrow y=-14\)

Vậy ..........................

\(\frac{x}{10}=\frac{y}{7}=\frac{x.y}{10.7}=\frac{280}{70}=4\)

\(\Rightarrow x=4.10=40\)

\(y=4.7=28\)

~~~~~~~~~

ai giúp k cho

a) x = 278.           

b) x = 295.          

c) x = 100.           

d) x = 180.

a) x = 278.

b) x = 295.

c) x = 100.

d) x = 180