Answer
(a) 90, see the table below
(b) $y=-x^2+19x$
(c) $90.25$
Work Step by Step
(a) see the table, the maximum is 90 when the two numbers are 9 and 10.
(b) Assume the first number is $x$, the second number is then $10-x$, their product $y$ is then
$y=x(19-x)=-x^2+19x$
(c) The maximum of this function happens at $x=\frac{19}{2}=9.5$ and $y=90.25$
This value is slightly larger than the estimate from (a)
