a) `123 - 27 + 27 + 13 - 123`

`= (123 - 123) + (27 - 27) + 13`

`= 0 + 0 + 13`

`= 13`

`---`

b) `175 + 25 + 13 + 15 - 175 - 25`

`= (175-175)+(25-25)+25+13`

`=0+0+25+13`

`=28`

`---`

c) \(53\times39+47\times39+53\times21+47\times21\)

\(=\text{[}\left(53+47\right)\times39]+\left[\left(53+47\right)\times21\right]\)

\(=\left(100\times39\right)+\left(100\times21\right)\)

\(=3900+2100\)

`=6000`

`---`

d) \(49\times35+49\times16-49\times61\)

`=` \(49\times\left(35+16-61\right)\)

`=` \(49\times\left(-10\right)\)

`=-490`

\(1,\\ a,\Leftrightarrow4^{5-x}=4^2\Leftrightarrow5-x=2\Leftrightarrow x=3\\ b,\Leftrightarrow\left[{}\begin{matrix}x-1=5\\x-1=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=6\\x=-4\end{matrix}\right.\\ c,\Leftrightarrow2x+1=3\Leftrightarrow x=2\\ 2,\\ a,3^{100}=\left(3^2\right)^{50}=9^{50}\\ b,2^{98}=\left(2^2\right)^{49}=4^{49}< 9^{49}\\ c,5^{30}=5^{29}\cdot5< 6\cdot5^{29}\\ d,3^{30}=\left(3^3\right)^{10}=27^{10}>8^{10}\\ 4,\\ a,\Leftrightarrow5\left(x-10\right)=10\\ \Leftrightarrow x-10=2\Leftrightarrow x=12\\ b,\Leftrightarrow3\left(70-x\right)+5=92\\ \Leftrightarrow3\left(70-x\right)=87\\ \Leftrightarrow70-x=29\\ \Leftrightarrow x=41\\ c,\Leftrightarrow16+x-5=315-230=85\\ \Leftrightarrow x=74\\ d,\Leftrightarrow2^x-5+74=707:\left(16-9\right)=707:7=101\\ \Leftrightarrow2^x=32=2^5\\ \Leftrightarrow x=5\)

X=(1800+600):30):560:(315:35)

X=(2400:30):560:9

X=80:560:9

X=80x1/560x1/9

X=1/7x1/9

X=1/63

A=58x72+63x81-58x52-63x61

  = (58x72-58x52)+(63x81-63x61)

  = 58(72-52)+63(81-61)

  = 58x20+63x20

  = 1160+1260

  = 2420

B=87x96-27x13+13x27-87x86

  = (87x96-87x86)-(27x13-13x27)

  = 87(96-86)-27(13-13)

  = 87x10 - 27x0

  = 870-0

  = 870

C= 53x39+87x39-53x31-47-21

  = (53x39+87x39)-(53x31+47+21)

  = 39(53+87)-(53x31+68)

  = 39x140 - 53x31 -68

  = 5460 - 1643 - 68

  = 3749

Hơi dài nên mình ko làm 

a) 35.(x-10)=35

         x-10= 35:35

         x-10= 1

             x= 1+10

            x= 10

b) 21.(32-x) =21

          32-x = 21:21

          32-x = 1

               x= 32-1

                x= 31

a)\(35.\left(x-10\right)=35\Rightarrow x-10=35:35=1\Rightarrow x=10+1=11\)

b) \(21.\left(32-x\right)=21\Rightarrow32-x=21:21=1\Rightarrow x=32-1=31\)

c) \(25.\left(2x.4\right).12=0\Rightarrow25.\left(2x.4\right)=0:12=0\Rightarrow2x.4=0:25=0\)

\(\Rightarrow2x=0:4=0\Rightarrow x=0:2=0\)

a) 6x - 35 + 5x - 21 = (6x + 5x) - (35 + 21) = 11x - 56 = 17x - 20 => 11x = 17x - 20 + 56 = 17x + 36

=> 36 = 11x - 17x = -6x => x = 36 : (-6) = -6

b) 5x + 35 - 4x - 27 = (5x - 4x) + (35 - 27) = x + 8 = 14x + 34 => x = 14x + 34 - 8 = 14x + 26

=> 26 = x - 14x = -13x => x = 26 : (-13) = -2

(6x+5x)+(-35-21)=17x-20

11x-56=17x-20

11x-17x=-20+56

-6x=36

x=36/-6

x=-6

vậy x=-6

a) \(6x-35+5x-21=17x-20\)

\(\Rightarrow6x-25+5x-21+20=17x\)

\(\left(6x+5x\right)+\left(20-25-21\right)=17x\)

\(11x+\left(-36\right)=17x\)

\(17x-11x=-36\)

\(6x=-36\)

\(x=\frac{-36}{6}=-6\)

Vậy \(x=-6\)

b) \(5x+35-4x-27=14x+34\)

\(\Rightarrow5x+35-4x-27-34=14x\)

\(\left(5x-4x\right)+\left(35-27-34\right)=14x\)

\(x+\left(-26\right)=14x\)

\(14x-x=-26\)

\(13x=-26\)

\(x=-\frac{26}{13}=-2\)

Vậy \(x=-2\)

a: Đặt D(x)=0

=>(3x+9)(2x-1)=0

=>x=-3 hoặc x=1/2

b: Đặt E(x)=0

=>(x-5)(x+5)=0

=>x=5 hoặc x=-5

c: Đặt F(x)=0

=>4x(x+2)=0

=>x=0 hoặc x=-2

A = 78 x 31 + 78 x 24 + 78 x 17 + 22 x 72

A = 78 x ( 31 + 24 + 17 ) + 22 x 72

A = 78 x 72 + 22 x 72

A = 72 x ( 78 + 22 ) 

A = 72 x 100

A = 7200

C = 53 x 39 + 47 x 39 - 53 x 21 - 47 x 21

C = 39 x ( 53 + 47 ) - 21 x ( 53 - 47 )

C = 39 x 100 - 21 x 6

C = 3900 - 126

C = 3774

ko pc tui thua bn 1 lp 

A = 78 x 31 + 78 x 24 + 78 x 17 + 22 x 72

A = 78 x ( 31 + 24 +17 ) + 22 x 72

A = 78 x 72 + 22 x 72

A = 72 x ( 78 + 22 )

A = 72 x 100

A = 7200