8X5000 is 40000. There's three zeroes in5000 and no zeroes in 8, yet there are 4 zeroes in the answer. This is because you must multiply the non-zeroes, and then add the zeroes from your factors. 8 times 5 is 40, add 3 zeroes to get 40000. Hope this helps!
The answer is going to be 2*sqrt(5). You have to split it into perfect squares for it to be simplified... so in this case, I had sqrt(4*5) because sqrt(4) can be simplified... so your answer would be sqrt(4)*sqrt(5) or 2sqrt(5)