x - the first number15 - x - the second numberx(15 - x) - the product of the our numbers
f(x) = -x^2 + 15x
The maximum value is in the vertex of parabola (h; k).
For ax² + bx + c:
[tex]h=\dfrac{-b}{2a};\ k=f(h)=\dfrac{b^2+4ac}{4a}[/tex]
We have: a = -1; b = 15; c = 0
substitute:
[tex]h=\dfrac{-15}{2\cdot(-1)}=\dfrac{15}{2}=7.5[/tex]
15 - 7.5 = 7.5
Answer: 7.5 and 7.5.
