Question 188563
I understood that we have the following:

4(sqrt{2} - 8(sqrt{10})(sqrt{5})

I would multiply 8(sqrt{10})(sqrt{5}) as step one.

Doing so, we get 8(sqrt{50}), which is then reduced to 8 times 5 times sqrt{2}.

Of course, this leads to 40(sqrt{2}).

Our subtraction now looks like this:

4(sqrt{2}) - 40(sqrt{2}).  

The goal is to get the same number in the radicand, which I have done.  Do you see that each radicand now has a 2?  We can now proceed to subtract.

Final answer: -36(sqrt{2})

Understand?