[size=150]Think of algebraic terms as areas of rectangles[br]For example [math]a\left(x+b\right)[/math] would be the area of a rectangle with length [math]x+b[/math] and breadth [math]a[/math].[br]When the rectangle is divided into two, along its length [math]x+b[/math], such that one has the length [math]x[/math] while the other has the length [math]b[/math] then there are two rectangles.[br]The areas of the rectangles [math]ax[/math] and [math]ab[/math] respectively. [br]Hence the original area [math]a\left(x+b\right)[/math] is equal to the sum of areas of the two rectangles [math]ax+ab[/math] .[/size]