Like what you saw?
Create FREE Account and:
 Watch all FREE content in 21 subjects(388 videos for 23 hours)
 FREE advice on how to get better grades at school from an expert
 Attend and watch FREE live webinar on useful topics
Difference of Perfect Squares  Problem 2
Alissa Fong
Alissa Fong
MA, Stanford University
Teaching in the San Francisco Bay Area
Alissa is currently a teacher in the San Francisco Bay Area and Brightstorm users love her clear, concise explanations of tough concepts
This is a difference of perfect squares problem that’s a little bit different because my leading coefficient isn’t 1, I start out here with 16. But I’m still going to use the same process. I know if I have the difference of perfect squares, it's equal to a plus b times a minus b, plus and minus with my two square roots. So here if I take the square root of 16x² that’s going to be 4x, that will be the fist term in each one of my factors, then I need to take the square root of 81, that’s 9. I’ll have plus 9 and minus 9. That’s it, that’s my final answer.
Again you could write this as 4x minus 9 and plus or you could still switch this and it’s still the same answer because with multiplying it doesn’t matter which one comes first or second.
The key is making sure you take the square root of this first term and the square root of the second term and then writing it with pluses and minuses in between them.
Please enter your name.
Are you sure you want to delete this comment?
Alissa Fong
M.A. in Secondary Mathematics, Stanford University
B.S., Stanford University
Alissa has a quirky sense of humor and a relatable personality that make it easy for students to pay attention and understand the material. She has all the math tips and tricks students are looking for.
Your tutorials are good and you have a personality as well. I hope you have more advanced college level stuff, because I like the way you teach.”
Thanks alot for such great lectures... I never found learning this easier ever before... keep up the great work.... :)”
You seem so kind, it's awesome. Easier to learn from people who seem to be rooting for ya!' thanks”
Concept (1)
Sample Problems (8)
Need help with a problem?
Watch expert teachers solve similar problems.

Difference of Perfect Squares
Problem 1 6,987 viewsFactor:
x² − 16 
Difference of Perfect Squares
Problem 2 6,351 viewsFactor:
16x² − 81 
Difference of Perfect Squares
Problem 3 5,364 viewsFactor:
x⁶ − 4y² 
Difference of Perfect Squares
Problem 4 847 views 
Difference of Perfect Squares
Problem 5 773 views 
Difference of Perfect Squares
Problem 6 752 views 
Difference of Perfect Squares
Problem 7 857 views 
Difference of Perfect Squares
Problem 8 877 views
Comments (0)
Please Sign in or Sign up to add your comment.
·
Delete