Respuesta :

gmany

b - the base

h = b + 3 - the height

The formula of an area of a triangle:

[tex]A=\dfrac{1}{2}bh[/tex]

Substitute:

[tex]A(b)=\dfrac{1}{2}b(b+3)=\dfrac{1}{2}(b^2+3b)\to\boxed{A.}[/tex]