You can put this solution on YOUR website! This is binomial:
(a+b)^n
http://www.intmath.com/series-binomial-theorem/4-binomial-theorem.php
in this case 1 = a, -2x is b and 6 is n
(a+b)^n
See how (x2 - 2y)5 has been expanded
http://www.intmath.com/series-binomial-theorem/4-binomial-theorem.php
One easy way to solve (49/50)^6 is open and Excel sheet and in one of the cells type
=(49/50)^6
You will get .886