Help I've been stuck on this!! (Please explain it in depth if you can) 3^2013-3^2012

It says it is equal to 2x3^2012, but I don't understand how exactly it is equal to that.

For the rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78. for an 10 month period, the last term is and the series sum is . for a 15 month period, the last term is and the series sum is . for a 20 month period, the last term is and the series sum is

Rectangle leg this 11feet and perimeter of 38feet what is the width of the rectangle in feet

Complex numbers multiply √-4 * √-25 and show all intermediate steps. alternative notation is sqrt(-4) * sqrt(-25).