a: Ta có: \(\left(x+3\right)\left(x-3\right)-\left(x-2\right)\left(x+5\right)=6\)

\(\Leftrightarrow x^2-9-x^2-3x+10=6\)

\(\Leftrightarrow-3x=5\)

hay \(x=-\dfrac{5}{3}\)

c: \(4x^2-9=0\)

\(\Leftrightarrow\left(2x-3\right)\left(2x+3\right)=0\)

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

\(a,\Leftrightarrow x^2-9-x^2-3x+10=6\\ \Leftrightarrow-3x=5\Leftrightarrow x=-\dfrac{5}{3}\\ b,\Leftrightarrow2x^2+3x^2-3=5x^2+5x\\ \Leftrightarrow5x=-3\Leftrightarrow x=-\dfrac{3}{5}\\ c,\Leftrightarrow\left(2x-3\right)\left(2x+3\right)=0\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{3}\\x=-\dfrac{2}{3}\end{matrix}\right.\\ d,\Leftrightarrow\left(5-2x\right)^2-4=0\\ \Leftrightarrow\left(5-2x-2\right)\left(5-2x+2\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\x=\dfrac{7}{2}\end{matrix}\right.\\ e,\Leftrightarrow\left(x-3\right)\left(2x+5\right)=0\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-\dfrac{5}{2}\end{matrix}\right.\)

\(f,\Leftrightarrow\left(2x+9\right)\left(x-2\right)=0\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-\dfrac{9}{2}\end{matrix}\right.\\ g,\Leftrightarrow\left(x^2-4\right)\left(3x-4\right)=0\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-2\\x=\dfrac{4}{3}\end{matrix}\right.\\ h,\Leftrightarrow\left(x+1\right)\left(x^4+x^2+1\right)=0\\ \Leftrightarrow\left(x+1\right)\left(x^4+2x^2+1-x^2\right)=0\\ \Leftrightarrow\left(x+1\right)\left(x^2+x+1\right)\left(x^2-x+1\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=-1\\\left(x+\dfrac{1}{2}\right)^2+\dfrac{3}{4}=0\left(vô.lí\right)\\\left(x-\dfrac{1}{2}\right)^2+\dfrac{3}{4}=0\left(vô.lí\right)\end{matrix}\right.\Leftrightarrow x=-1\)

x = 1

x = 0

=> x-2007+y-2008 = x+y−4015≤0

=> x+y≤4015

 => => x lần lượt là 0,1,2,3,.....4015 và y lần lượt là: 4015;4014;.....;1;0

=x+x+1+x-2+11=6x+1
=1-2+11-1=-x-x-x+6x
9=3x
x=3

x : 9= 12

      x=12 . 9

       x=   108

chúc bạn học tốt!!

x : 9 = 12 

    x  = 12 x 9 

    x  = 108

x : 9 = 12

     x = 12 x 9

     x = 108

Chúc bạn học giỏi nha

Ta có :

| 2 + 3x | - | 4x - 3 | = 0

\(\Rightarrow\)| 2 + 3x | = | 4x - 3 |

\(\Rightarrow\)2 + 3x = \(\pm\)( 4x - 3 )

Ta xét 2 trường hợp :

Th 1 :

2 + 3x = 4x - 3

3x - 4x = - 3 - 2

- x = - 5

\(\Rightarrow\)x = 5

Th 2 :

2 + 3x = - ( 4x - 3 )

2 + 3x = - 4x + 3

3x + 4x = 3 - 2

7x = 1

\(\Rightarrow\)x = \(\frac{1}{7}\)

Vậy x \(\in\){ 5 ; \(\frac{1}{7}\)}

Dương hay nguyên dương vậy ??

Nếu nguyên dương thì : 

\(\frac{1}{x}+\frac{1}{y}=\frac{1}{5}\) => \(\frac{1}{x}=\frac{y-5}{5y}\)=> \(x=\frac{5y}{y-5}=\frac{5\left(y-5\right)+25}{y-5}=5+\frac{25}{y-5}\)

Vì x nguyên nên \(\frac{25}{y-5}\inℤ\)=> \(y-5\inƯ\left(25\right)=\left\{1;-1;5;-5;25;-25\right\}\)

Giải ra ta tìm được x, thay vào pt đề ra tìm đc y bạn tự làm nk