a)9 (3x - 2) = x ( 2- 3x)

   9 (3x - 2) - x ( 2- 3x) = 0

    9 (3x - 2) + x ( 3x-2 ) = 0

     ( 9 + x )( 3x - 2 ) = 0

\(\Rightarrow\orbr{\begin{cases}9+x=0\\3x-2=0\end{cases}\Rightarrow}\orbr{\begin{cases}x=-9\\x=\frac{2}{3}\end{cases}}\)

b)x³ - 0,25x = 0 

   x(x²-0,25)=0

Suy ra x=0

9( 3x-2)= x(2-3x)

<=> 9(3x-2)= - x(3x-2)

<=> \(\frac{-x}{9}\)= \(\frac{3x-2}{3x-2}\)

<=> \(\frac{-x}{9}\)= 1

<=> -x=9

<=> x=-9

b, x^3-0,25x =0

<=> x(x^2-0,25)= 0

<=> x=0 <=> x=0 <=> x=0

hoặc x^2- 0,25 =0 <=> x^2=0,25 <=> x= 0,5

                                                 hoặc x= -0,5

= \(\left[\frac{x.\left(x+3\right)}{\left(x+3\right).\left(x^2+9\right)}+\frac{3}{x+9}\right]:\left[\frac{1}{x-3}-\frac{6x}{\left(x-3\right)\left(x^2+9\right)}\right]\) ]

 \(=\frac{x+3}{x^2-9}.\frac{\left(x-3\right).\left(x^2+9\right)}{x^2+9-6x}\)

= \(\frac{\left(x-3\right).\left(x+3\right)}{\left(x-3\right)^2}\)

= \(\frac{x+3}{x-3}\)

k mik nhé. Plssss~

(x+2)^2-(x-2)(x+2)=0

=> (x+2)(x+2-x+2)=0

=> (x+2).4=0

=> x+2=0

=> x=-2

mấy câu còn lại tự làm nha

a) (x+2)^2-(x-2)(x+2)=0 

 (x+2).[x+2-x+2]=0

(x+2).4=0

 x+2=0

x=-2

 b)(2x - 1)^2 - (2x + 5) (2x - 5 ) = 18

   4x²-4x+1-4x²+25=18

   26-4x=18

   4x=8

    x=2

 c)( 2x - 1)^2 - 25 = 0

    ( 2x - 1)^2 - 5² = 0

     (2x-1-5)(2x-1+5)=0

    (2x-6)(2x+4)=0

\(\Rightarrow\orbr{\begin{cases}2x-6=0\\2x+4=0\end{cases}}\)\(\Rightarrow\orbr{\begin{cases}x=3\\x=-2\end{cases}}\)

\(M=\frac{1}{x^2-2xy+3}=\frac{1}{x^2-2xy+1+2}=\frac{1}{\left(x-1\right)^2+2}\)

Vì \(\left(x-1\right)^2\ge0\Rightarrow\left(x-1\right)^2+2\ge2\Rightarrow M=\frac{1}{\left(x-1\right)^2+2}\le\frac{1}{2}\)

M đạt giá trị lớn nhất <=> \(M=\frac{1}{2}\) <=> (x-1)²=0 <=> x-1=0 <=> x=1

Vậy \(M_{max}=\frac{1}{2}\) khi x=1

sai rồi kìa Trà My

Ta có:(x⁴+y⁴)=(x²+y²)²-2.x².y²

                    =(x²+y²)²-2.xy.xy

                     =15²-2.6.6

                     =225-72

                     =153

x^2+ y^2 = 15 => x^4 + 2x^2.y^2 + y^4 = 225 

        <=>             x^4 + 2.6^2 + y^4      = 225 

        <=>               x^4 +  y^4               = 153