Let $x$ and $y$ be nonnegative real numbers. If $x + y = 25$, then find the minimum value of $6x + 3y.$
Our first step is to isolate y from the first equation. Moving x to the other side, we get
y=25−x
Now, we plug this value of y into the second equation. We get
6x+3(25−x)6x+75−3x3x+75
Now, x has to be nonegative, so it cannot be a negative number. The next smallest number is 0.
Plugging in the value of 0, we get
3(0)+7575
So 75 is our final answer!
Thanks! :)