Learn math, science, English SAT & ACT from
highquaility study
videos by expert teachers
Thank you for watching the preview.
To unlock all 5,300 videos, start your free trial.
Solving Quadratic Equations Using Square Roots  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
Here I have a quadratic equation with no b term so right away I’m thinking I’m going to want to take the square root of both sides of an equation but first I want to get x isolated. I’m going to have to get rid of this 81 piece by adding 81 to both sides, 100x² equals 81.
Next thing I want to do is to get rid of that 100. I’m going to divide both sides by 100 so that I have x² equals 81 over 100. Okay I’m almost there in order to have regular old x and not x² I need to square root both sides. X is going to be equal to the positive and negative square root of 81 over 100.
So depending on what your textbook says you might grab a calculator and do that on your calculator or you might be able to know in your head that the square root of 81 over 100 is 9 over 10. So x is going to be equal to positive and negative 9/10.
The way I would check that is by substituting in one at a time positive 9/10 and then negative 9/10 here and making sure that’s equal to 0.
So guys these problems aren’t too bad if there’s no b term just undo everything that’s been done to x including taking the square root of both sides at the end.
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.
Sample Problems (14)
Need help with a problem?
Watch expert teachers solve similar problems.

Solving Quadratic Equations Using Square Roots
Problem 1 11,651 viewsSolve:
x² − 225 = 0 
Solving Quadratic Equations Using Square Roots
Problem 2 10,611 viewsSolve:
100x² − 81 = 0 
Solving Quadratic Equations Using Square Roots
Problem 3 8,725 viewsSolve:
x² + 36 = 0 
Solving Quadratic Equations Using Square Roots
Problem 4 1,773 views 
Solving Quadratic Equations Using Square Roots
Problem 5 1,598 views 
Solving Quadratic Equations Using Square Roots
Problem 6 631 views 
Solving Quadratic Equations Using Square Roots
Problem 7 744 views 
Solving Quadratic Equations Using Square Roots
Problem 8 655 views 
Solving Quadratic Equations Using Square Roots
Problem 9 659 views 
Solving Quadratic Equations Using Square Roots
Problem 10 490 views 
Solving Quadratic Equations Using Square Roots
Problem 11 555 views 
Solving Quadratic Equations Using Square Roots
Problem 12 494 views 
Solving Quadratic Equations Using Square Roots
Problem 13 480 views 
Solving Quadratic Equations Using Square Roots
Problem 14 548 views
Comments (0)
Please Sign in or Sign up to add your comment.
·
Delete