Given that A=(2008+2009),B=(−2008−2009),C=(2008−2009), and D=(2009−2008), find ABCD.
Solution — click to reveal
We can use difference of squares to see that (2009+2008)(2009−2008)=2009−2008=1 Also, (−2009+2008)(−2009−2008)=2009−2008=1 So the product is 1.