The square root of x is the number whose square is x; the cube root is the number whose cube is x.
1Rules
√(ab) = √a × √b, √(a/b) = √a/√b
A perfect square ends in 0, 1, 4, 5, 6 or 9; it never ends in 2, 3, 7 or 8
Square root of a decimal: make the number of decimal places even, then halve it
2Nearest perfect square
Least number to subtract to make n a perfect square = n − ⌊√n⌋²
Least number to add = ⌈√n⌉² − n