Answer:

Explanation:
Simplify the radicand by splitting the number into two numbers, one of which is a perfect square (like 4, 9, 16, 25, 36, 49, 64, 81, 100*).
Factors of 448 that include a perfect square: 7 and 64**. Split:

Therefore, A is 8 and B is 7.
:Done
Notes:
*Perfect squares:

Make sure to use the number in the radical symbol, not the simplified number.
**You can find factors with a perfect square by dividing the radicand by perfect squares. The bigger the number, the better. I started at 100:
448÷100=4.48
448÷81=5.530864197
448÷64=7
Stop when you find one that results in a whole number, like 7. The result and perfect square are the factors.