√12
First find the highest perfect square that can go into it.
1, 4, 9, 16
The highest square is 4 (2^2)
To take out 4 from √12, put the root of four multiplied by the root of the quotient of 12 and 4 (the quotient of 12 and 4 should become the radicand).
Final answer: 2√3