The equation which represents the situation is:
[tex]x^2+6x-256=0[/tex]
Let x represent the width of the rectangle in centimeters.
The length of a rectangle is 6 cm more than its width.
This means that the length of the rectangle is: x+6 cm.
Also, we know that the area of a rectangle is the product of the length and width of the rectangle.
Here, the area of the rectangle is 256 cm².
i.e.
[tex]x(x+6)=256\\\\x^2+6x=256\\\\i.e.\\\\x^2+6x-256=0[/tex]