Square Roots and Radicals
A square root is defined as a number which when multiplied by itself gives a real
non-negative number called a square.
A square root is best defined using geometry where, considering a square (which
is a four sided polygon whose sides are all equal), a square root is defined as
the length of the diagonal of this square (a diagonal is a line drawn from one vertex/corner
to the opposite vertex of the square).
A radical is a root of a number. A square root is a radical. Roots can be square
roots, cube roots, fourth roots and so on.
A square root is commonly shown as
is known as the radical sign and
is known as the radicand.
A square root of a number can also be represented as
and a radical as
where we say that in the above, we’re finding the nth root of x. For
more on the above notation, refer to section on
A radical can also be represented as
A square root is also represented as
A cube root as
A fourth root as
Every square has two square roots; one positive and the other negative. This is
which is written as
This can be proved in the following way. Consider a number, a
the latter is because a negative multiplied by a negative equals a positive.
And so it follows that
Thus it follows that any real positive number has two roots. But when talking about
in other words,
only refers to +x which is known as the principal square root. So despite
having said above that
we usually only consider
especially if the
But if the question asked is in the form
always give both the positive and negative roots, i.e.
Although any real positive number can be considered a square number and thus has
a square root, we only consider numbers with whole number square roots as squares.
Properties of Square Roots and Radicals
Properties of square roots and radicals guide us on how to deal with roots when
they appear in algebra.
Examples of Square Roots and Radicals
Evaluate the following:
The above is left as is, unless you are specifically asked to approximate, then
you use a calculator.
Quiz on Square Roots and Radicals
The answer is obtained as follows:
First factor out both the numerator and denominator into numbers whose square roots
are easy to find
From here you can cancel the terms that appear in both the numerator and denominator: