Question 1144509
x, base
y, height
A, area


{{{system(A=(1/2)xy,x+y=18)}}}

{{{A=(1/2)x(18-x)}}}
The maximum occurs at the vertex, which is exactly in the middle of the two zeros of A.


{{{(1/2)x(18-x)=0}}}
{{{zeros}}}{{{at}}}{{{0}}}{{{and}}}{{{18}}};
A is maximum at x=9 and y=9.