February 23, 2017

Homework Help: Math (Trigenometry)

Posted by Anonymous on Tuesday, February 8, 2011 at 7:30pm.

Find two positve real numbers whose product is a maximum and whose sum of the first number and four times the second number is 120.

This is as far as I've gotten in solving it.

*first number is x.
*second number is y.
*xy=maximum, which is unknown.
*x+4y=120. Solve for x, which comes out to be x=-4y+120.
*Substitute -4y+120 for x in the equation xy, then solve for y. So (-4y+120)(y) = -4y(y-30) = y=0 and y=30.
Please show me what to do from here.

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