5x + x = 3¹⁹ : 3¹⁸ + 21

   6x    =     3 + 21

    6x  =        24

      x =  24 : 6

      x =     4

cảm ơn bạn nhá tobot z

B

A. -18

A

@Nguyễn Việt Lâm em sắp ktra, anh giúp em bài này với ạ ....

Akai Haruma giúp em giải phương trình trên được ko ạ ^_^

@Nguyễn Việt Lâm anh giải bải này đc ko ạ .

a) Ta có: \(\frac{x-17}{33}+\frac{x-21}{29}+\frac{x}{25}=4\)

\(\Leftrightarrow\frac{x-17}{33}-1+\frac{x-21}{29}-1+\frac{x}{25}-2=0\)

\(\Leftrightarrow\frac{x-17-33}{33}+\frac{x-21-29}{29}+\frac{x-2\cdot25}{25}=0\)

\(\Leftrightarrow\frac{x-50}{33}+\frac{x-50}{29}+\frac{x-50}{25}=0\)

\(\Leftrightarrow\left(x-50\right)\left(\frac{1}{33}+\frac{1}{29}+\frac{1}{25}\right)=0\)

Vì \(\frac{1}{33}+\frac{1}{29}+\frac{1}{25}>0\)

nên x-50=0

hay x=50

Vậy: x=50

b) Ta có: \(\left(3x-5\right)\left(7-5x\right)+\left(5x+2\right)\left(3x-2\right)=2\)

\(\Leftrightarrow-15x^2+46x-35+15x^2-4x-4-2=0\)

\(\Leftrightarrow42x-41=0\)

\(\Leftrightarrow42x=41\)

hay \(x=\frac{41}{42}\)

a, \(\frac{x-17}{33}+\frac{x-21}{29}+\frac{x}{25}=4\)

\(\Leftrightarrow\left(\frac{x-17}{33}-1\right)+\left(\frac{x-21}{29}-1\right)+\left(\frac{x}{25}-2\right)=4-4\)

\(\Leftrightarrow\left(\frac{x-17-33}{33}\right)+\left(\frac{x-21-29}{29}\right)+\left(\frac{x-2.25}{25}\right)=0\)

\(\Leftrightarrow\frac{x-50}{33}+\frac{x-50}{29}+\frac{x-50}{25}=0\)

\(\Leftrightarrow\left(x-50\right)\left(\frac{1}{33}+\frac{1}{29}+\frac{1}{25}\right)=0\) (*)

Vì \(\frac{1}{33}+\frac{1}{29}+\frac{1}{25}>0\Rightarrow\) Phương trình (*) xảy ra khi: \(x-50=0\Leftrightarrow x=50\)

Vậy phương trình có nghiệm duy nhất là x = 50.

a) -x-18=12

     -x=12+(-18)

     -x=-6

 =>x=6

-x - 18 = 12

        -x = 12 + 18

        -x = 30

         x = -30

3x - 5 = x + 11

3x - x = 5 + 11

     2x = 16

       x = 8

-39 + x + 165 = -19 + 165

       126 + x = 146

                x = 146 - 126

                x = 20

c)-39+x+165=-19+165

    -39+x+165=146

     -39+x=146-165

     -39+x=-19

            x=-39-(-19)

            x=-20

     k mik nha đang âm điểm

bạn tự kl nhé 

a, \(\left|x+5\right|=3x+1\)

TH1 : \(x+5=3x+1\Leftrightarrow-2x=-4\Leftrightarrow x=2\)

TH2 : \(x+5=-3x-1\Leftrightarrow4x=-6\Leftrightarrow x=-\dfrac{3}{2}\)( ktm )

b, \(\left|-5x\right|=2x+21\)

TH1 : \(5x=2x+21\Leftrightarrow3x=21\Leftrightarrow x=7\)

TH2 : \(5x=-2x-21\Leftrightarrow7x=-21\Leftrightarrow x=-3\)

khó nhìn quá ko

a) Ta có: |x+5|=3x+1

\(\Leftrightarrow\left[{}\begin{matrix}x+5=3x+1\left(x\ge-5\right)\\x+5=-3x-1\left(x< -5\right)\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x-3x=1-5\\x+3x=-1-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}-2x=-4\\4x=-6\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=2\left(nhận\right)\\x=-\dfrac{3}{2}\left(loại\right)\end{matrix}\right.\)

Vậy: S={2}

\(\dfrac{21}{16}\times\dfrac{8}{5}\times\dfrac{15}{7}=\dfrac{21\times8\times15}{16\times5\times7}=\dfrac{7\times3\times8\times5\times3}{8\times2\times5\times7}=\dfrac{3\times3}{2}=\dfrac{9}{2}\)

\(\dfrac{18}{9}\times\dfrac{9}{36}\times\dfrac{27}{3}=2\times\dfrac{1}{4}\times9=\dfrac{1}{2}\times9=\dfrac{9}{2}\)

b) \(-x^2-12x+21=\left(3-x\right)\left(x+11\right).\)

\(\Leftrightarrow-x^2-12x+21=-x^2-8x+33\)

\(\Leftrightarrow33+4x=21\)

\(\Leftrightarrow-4x=12\)

\(\Rightarrow x=-3\)

c,\(9x+5x^2+1=5x^2-22+13x\)

\(\Leftrightarrow4x-22=1\)

\(\Leftrightarrow4x=23\)

\(\Rightarrow x=\frac{23}{4}\)

Mk làm mẫu cho 1 pt nha !

a, 

pt <=> 4x^2-7x+5 = 2x^2-5x-18 

<=> (4x^2-7x+5)-(2x^2-5x-18) = 0

<=> 4x^2-7x+5-2x^2+5x+18 = 0

<=> 2x^2-2x+23 = 0

<=> x^2-x+23/2 = 0

<=> (x^2-x+1/4)+45/4 = 0

<=> (x-1/2)^2+45/4 = 0

=> pt vô nghiệm [ vì (x-1/2)^2+45/4 > 0 ]

P/S: Tham khảo nha