Is this statement false, how do i make it true?

All of the adjacent sides of quadrilaterals have slopes with a product of -1?Is this statement false, how do i make it true?
False. For the product of slopes to be -1, the lines must be perpendicular, and there are quadrilaterals with adjacent sides that are not perpendicular.





A less incorrect statement would be that all the adjacent sides of rectangles have slopes with a product of -1, since in the case of a rectangle the adjacent sides will be perpendicular (in fact, this is essentially the definition of a rectangle). However, even this statement is wrong, since the theorem regarding the product of the slopes of perpendicular lines only applies if both slopes are defined -- if one of the lines is vertical, the slope is undefined, and so is the product of the two slopes.





A correct statement would be: All of the adjacent sides of a rectangle having no vertical sides have slopes with a product of -1.Is this statement false, how do i make it true?
Got me, True???