What Is a Radical?
Definition
Radical: A number written with a root sign, such as √2 or 6√5. In a√b, a is the coefficient outside the root and b is the radicand; in simplest form, b has no square factor.
A radical is a number written with a root sign, such as √2, √5 or 6√2. When the number under the sign is not a perfect square, the root stays in radical form. In a√b, a is the coefficient and b is the radicand, the number under the root. In simplest form, b has no square factor.
Where it appears in the formulas
The square root calculator gives a radical in the form √x = a × √b. For √72 the coefficient is 6 and the radicand is 2: √72 = 6 × √2. √72 = 2 × √18 is also true but not the simplest form, because 18 still contains 9 = 3².