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Algebra 1
Course: Algebra 1 > Unit 11
Lesson 3: Simplifying square rootsSimplifying square roots review
Learn how to rewrite square roots (and expressions containing them) so there's no perfect square within the square root. For example, rewrite √75 as 5⋅√3.
Simplifying square roots
Example
Let's simplify
We start by factoring
We found one! This allows us to simplify the radical:
So
Want another example like this? Check out this video.
Simplifying square roots with variables
Example
Let's simplify
First, we factor
Then, we find the greatest perfect square in
And now we can simplify:
More challenging square root expressions
Want to try more problems like these? Check out this exercise.
Want to join the conversation?
what grade maths would this be?(13 votes)
I think it’s about eighth or ninth grade. But people take math at different times. I’ve known fith graders who have taken algebra and geometry in the same year, and I’ve known ninth graders who have taken algebra. Even if you’re taking algebra in ninth grade, that’s okay. What really matters is that you understand the content when you learn it.(59 votes)
- when will we ever use this in everyday life? whats the point of even learning this?(12 votes)
Jaidyn,
After learning this helps you pass your Math class and graduate high school, there are many careers where this is used. Most obviously, it's used in engineering and computer science. However, when I worked in construction, I used to use square roots regularly to determine whether items would fit through a doorway on a diagonal. (Note: this also involves trigonometry.)(45 votes)
can a fraction be an exponent?(9 votes)
A fraction can be an exponent. When a fraction is an exponent, you can change it so that a there is a first, second, third, etc. root of something.
For example,
1^1/2 = square root of 1
1^1/3 = third root of 1
1^1/4 = fourth root of 1
And so on and so forth. This was covered in a series of videos in the topic Rational Exponents and Radicals.
https://www.khanacademy.org/math/algebra/rational-exponents-and-radicals/alg1-rational-exp-eval/v/fractional-exponents-with-numerators-other-than-1(10 votes)
Anyone else need to take like 4 or 5 hours to really get a firm understanding of this lesson? or am I just dumb?(11 votes)- Sometimes things snap right into place and the light goes on right away, and other times we need review and practice. If you got this far, you already have all the pieces you need to work with radicals. It's a matter of seeing how they go together.(2 votes)
golly gracious i think ive passed out 15 times trying to these(11 votes)- In the video "Simplifying square roots (variables)" @1:40Sal explains "as I said in the last video, the principal root of X squared is going to be the absolute value of X, just in case X is a negative number". I have two questions:
(1) Can anybody please point me to that video? I can't find it.
(2) I don't understand the need for an absolute value. If we state, before beginning to solve the problem, that the domain of the X variable is the Positive Real Numbers (or X greater than or equal to zero), aren't we already cancelling out the possibility that the X variable assumes a negative value by restricting the domain, thus rendering the use of the absolute value unnecessary?(9 votes) 
Can i also simplify √72 in this way: √72 = √9*8 = √9*√8 = 3√8
instead of: √72 = √2*36 = √36*√2 = 6√2(3 votes)
Yes, you can take that approach. But, your work is incomplete. When you simplify a square root, you need to ensure you have removed all perfect squares. With 3√8, you still have a perfect square inside the radical.
3√8 = 3√(4*2) = 3√4 * √2 = 3*2√2 = 6√2
Hope this helps.(9 votes)
- what about problems with a number already multiplying the square root. Do you multiply or add the numbers together?(4 votes)
It's easier to understand if there is an example. Let's say you have √98. 98 is 49*2 which is 7^2*2, it would be 7√2. If you have 2√98. √98 is 7√2, 2√98 would be 14√2.
Hope this helps! If you have any questions or need help, please ask! :)(7 votes)
- how do you do long division(0 votes)
let me show you an example: 129/343 three "goes in" 43 times
______
3|129
12 3 goes into 12 four times
-12 minus 3*4 (in between 12 and 0, and 3,0 there is a line)
09 remainder of 0. bring down the 9
3(16 votes)
- How can we solve a radical equation with another radical inside of it?(3 votes)
So are you saying something like √ (√x) = 2? This is a very simple one, so square both sides to get √x=4, do it a second time to get x = 16. The alternate way is to go into rational exponents so if you have the cube root of the square root of (x-5) =2, you get ((x-5)^(1/2))^1/3 = 2, power to power requires multiplication, so (x-5)^1/6 = 2, opposite of 1/6 is 6 in exponent, so (x-5)^(1/6*6)=2^6, x-5=64, x=69. It obviously can get much more complicated than this.(8 votes)
1:40