# Finding a number

• August 2nd 2006, 05:34 PM
pashah
Finding a number
Find two real numbers that differ by 5 and have a product of 16
• August 2nd 2006, 05:48 PM
ThePerfectHacker
Quote:

Originally Posted by pashah
Find two real numbers that differ by 5 and have a product of 16

You need that,
$x-y=5$
$xy=16$
Thus,
$x=y+5$
Thus,
$y(y+5)=16$
Thus,
$y^2+5y-16=0$
Thus,
$y=\frac{-5\pm \sqrt{25+64}}{2}$
• August 2nd 2006, 05:55 PM
Quick
I find it interesting how often the quadratic formula ends up being used
• August 2nd 2006, 05:58 PM
topsquark
Quote:

Originally Posted by Quick
I find it interesting how often the quadratic formula ends up being used

Trust me, if cubics were easier to solve we'd be seeing a lot more of those!

-Dan