Question 109481
The area of the rectangle is the product of the two sides.
{{{A=(x+4)(x-1)}}}
Using the FOIL (First Outer Inner Last) method,
{{{(x+4)(x-1)=x*x+(x)(-1)+(4)(x)+(4)(-1)}}}
{{{(x+4)(x-1)=x^2-x+4x-4}}}
{{{(x+4)(x-1)=x^2+3x-4}}}
{{{A=x^2+3x-4}}}