How can i prove that a^(m+n)=a^m*a^n

In factoring by grouping, what would you have for step 3 for the following? step 1: x^3 +5x^2 +4x+20 step 2: x^2 (x+5)+4(x+5) step 3: ?

Solve the system of equations y= 3/2 - 1, -x+ y =-3

Jose is going to use a random number generator 500500 times. each time he uses it, he will get a 1, 2, 3,1,2,3, or 44.