Ngu!

17x-28=12x-(-42)

17x-28=12x+42

5x-28=42

5x=24+42

5x=70

x=70/5

x=14

trả lời nhanh hộ mk vs

17x - 29 = 12x - (-42 )

17x - 12x = 29 - ( -42 )

5x = 29 + 42

5x = 71

  x = 71 : 5

  x = \(\frac{71}{5}\)

Ta có :

\(17x-28=12x-\left(-42\right)\)

\(\Leftrightarrow\)\(17x-12x=42+28\)

\(\Leftrightarrow\)\(5x=70\)

\(\Leftrightarrow\)\(x=14\)

Vậy \(x=14\)

Chúc bạn học tốt 

Bài làm

17x - 28 = 12x - ( -42 )

=> 17x - 28 = 12x + 42

=> 17x - 12x = 42 + 28

=> 5x = 70

=> x = 14

Vậy x = 14 

\(17x-28=12x-\left(-42\right)\)

\(17x-28=12x+42\)

\(17x-12x=42+28\)

\(5x=70\)

\(x=14\)

Vậy \(x=14\)

17x - 28 = 12x - ( - 42 )

<=> 17x - 28 = 12x + 42

<=> 17x - 12x = 42 + 28

<=> 5x = 70

<=> x = 14

\(\Leftrightarrow-12x+17x=20+2\\ \Leftrightarrow5x=22\\ \Leftrightarrow x=\dfrac{22}{5}\)

a)10²-(x-3)=4³

=>100-(x-3)=64

=>x-3=100-64

=>x-3=36

=>x=36+3

=>x=39

b)25²-(17x+82)=15²+132

=>625-(17x+82)=225+132

=>625-(17x+82)=375

=>17x+82=625-375

=>17x+82=250

=>17x=250-82

=>17x=168

=>x=168:17

=>x=168/17

c)20²-(28²-12x)=6²

=>40-(784-12x)=36

=>784-12x=40-36=4

=>12x=784-4=780

=>x=780:12=65

`G(x)+H(x)=(21x^2+1+17x)+(-2+6x^3-12x^2-8)`

`=21x^2+1+17x-2+6x^3-12x^2-8`

`= 6x^3+(21x^2-12x^2)+17x+(1-2-8)`

`= 6x^3+9x^2+17x-9`

`G(x)-H(x)=(21x^2+1+17x)-(-2+6x^3-12x^2-8)`

`= 21x^2+1+17x+2-6x^3+12x^2+8`

`= -6x^3+(21x^2+12x^2)+17x+(1+2+8)`

`= -6x^3+33x^2+17x+11`

`----`

`M(x)+N(x)=(7x^5 + 1 + 17x^4 - 2)+(6x^4 - 12x^2 - 23x^4 + x)`

`= 7x^5 + 1 + 17x^4 - 2+6x^4 - 12x^2 - 23x^4 + x`

`= 7x^5+(17x^4+6x^4-23x^4)-12x^2+x+(1-2)`

`= 7x^5-12x^2+x-1`

`M(x)-N(x)=(7x^5 + 1 + 17x^4 - 2)-(6x^4 - 12x^2 - 23x^4 + x)`

`= 7x^5 + 1 + 17x^4 - 2-6x^4 + 12x^2 + 23x^4 - x`

`= 7x^5+(17x^4-6x^4+23x^4)+12x^2-x+(1-2)`

`= 7x^5+34x^4+12x^2-x-1`

Mình đã trl rồi nha!

(https://hoc24.vn/cau-hoi/tinh-tong-avf-hieu-cac-da-thuc-saugx-21x2-1-17x-va-hx-2-6x3-12x2-8mx-7x5-1-17x4-2-va-nx-6x4-12x2-23x4-x.7858748287383)