Problem: width - x, length 800-2x How to find the width and length that will give the largest area

Question

Problem: width - x, length 800-2x   How to find the  width and length that will give the largest area

hartnn · Answer

do u know the formula for area in terms of width and length?

anonymous · Answer

yes x (800-2x), but I can't solve from there

hartnn · Answer

ok,to find largest area u should derivate area equation and equate it to zero....u know derivatives?

anonymous · Answer

not really

anonymous · Answer

not to butt in, but if you don't know calc you can still do it 
multiply out to get 
$$A(x)=800x-2x^2$$ max at the vertex

anonymous · Answer

explain max at the vertex.  This is Algebra 1

anonymous · Answer

$y=800x-2x^2$ is a parabola that opens down
the max is at the vertex and the first coordinate of the vertex is always 
$$x=-\frac{b}{2a}$$ in your case it is 
$$x=-\frac{800}{2\times -2}=200$$

anonymous · Answer

thank you. then x  is 200 (width) and length is 400

hartnn · Answer

yes it is :)

anonymous · Answer

thanks a bunch