Question 312323
The sum of an integer and three times another integer is 18. Determine the value of the two integers if their product is a maximum. Thanks!
What I have so far:
x + 3y = 18
x = 18 - 3y
Product = xy = y (18-3y)
Write it as a quadratic equation
f(y) = -3y^2 + 18y
Find the axis of symmetry using y = -b/(2a), where a=-3, b=18
y = {{{(-18)/(2*-3)}}}
y = {{{(-18)/(-6)}}}
y = +3
:
Find x
x = 18-3(3)
x = 9