At first find the area of rectangle:
(x + 4)*(x + 1) = x^2 + 5x + 4
Then find the area of triangle:
[tex] \frac{(x+1)(x-3)}{2} = \frac{x^2-2x-3}{2} [/tex]
Then you must do like this
Area of rectangle - Area of triangle = Area of the shaded
x^2+5x+4 - ([tex] \frac{x^2-2x-3}{2} [/tex])
