Question

Explain how to simplify 4 minus the square root of 28

Answer 1

4-sqrt(28)
4-sqrt(4*7)
4-2sqrt(7)

Answer 2

first see if 28 can be factored into any perfect squares (4,9,25 etc.)
since 28=4*7 you can take the square root of the 4 and out it out of the radical sign, as is done above by Zakaullah.