Skip main navigation

Roots and radicals in practice

Solving exercises about fundamental properties of root functions
10.1
Hello. We have to find the real numbers, a, such that this expression makes sense, and simplify it. OK. Remember that roots are defined only when the argument is a positive number. But since a to the 4th is greater or equal than 0 for any real number a, then our expression is defined–
57
is defined for all real numbers.
65.5
OK, let us try to simplify it. OK, let us write our expression–
76.3
in this form, first– it’s clear that 8 is 2 times 4. a to the 4th is exactly like to write, the module, of a to the 4th. And now we have the square. OK. Now we can simplify the expression inside, between brackets. And we get the square root of the module of a, and then to the square. And this now is equal to module of a.
135.8
We want to find all the real numbers for which this expression makes sense, and then try to simplify it. OK, this expression can be rewritten in the following way–
154.7
like the 6th root of a to 9 over the 3rd root of a. And now you know that roots are defined only for real numbers greater or equal than 0. But now we have also something in the denominator. And this has to be not equal to 0. Therefore, this expression is defined–
188.8
for all the real numbers a, greater than 0. And now, under this assumption, let us try to simplify this fraction. OK, we can write again this expression in the following form– as– the 6th root of a to the 9. And here we can write in this following form– the 6th root of a squared is exactly the same. And now we have the same order of roots in the numerator and the denominator. And we get the 6th root of a to the 9 over a to the square, which is equal to the 6th root of a to the 9 minus 2– a to the 7th power.

The following exercises are solved in this step.

We invite you to try to solve them before watching the video.

In any case, you will find below a PDF file with the solutions.

Exercise 1.

Find all the values of (a in mathbb R) for which the following expression makes sense and then simplify it: [left(sqrt[8]{a^4}right)^2]

Exercise 2.

Find all the values of (a in mathbb R) for which the following expression makes sense and then simplify it: [left(sqrt[3]{a}right)^{-1}sqrt[6]{a^9}]

Ex 3. [Solved only in the PDF file]

Sketch the graph of the function (f:xmapstosqrt[3]x).

This article is from the free online

Precalculus: the Mathematics of Numbers, Functions and Equations

Created by
FutureLearn - Learning For Life

Our purpose is to transform access to education.

We offer a diverse selection of courses from leading universities and cultural institutions from around the world. These are delivered one step at a time, and are accessible on mobile, tablet and desktop, so you can fit learning around your life.

We believe learning should be an enjoyable, social experience, so our courses offer the opportunity to discuss what you’re learning with others as you go, helping you make fresh discoveries and form new ideas.
You can unlock new opportunities with unlimited access to hundreds of online short courses for a year by subscribing to our Unlimited package. Build your knowledge with top universities and organisations.

Learn more about how FutureLearn is transforming access to education