SOLUTION: I am totally stumped at the end and need some help. 16x^4 - 40x^2 + 9 I have: (4x^2 -1) (4x^2 -9) and now I'm lost. Can someone help me to factor this completely where I can und

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: I am totally stumped at the end and need some help. 16x^4 - 40x^2 + 9 I have: (4x^2 -1) (4x^2 -9) and now I'm lost. Can someone help me to factor this completely where I can und      Log On


   

Question 103071: I am totally stumped at the end and need some help.
16x^4 - 40x^2 + 9
I have: (4x^2 -1) (4x^2 -9) and now I'm lost. Can someone help me to factor this completely where I can understand. Thank you.
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
You are obviously not "totally" stumped as your first step is definitely good.
Factor:
16x%5E4-40x%5E2%2B9+=+%284x%5E2-1%29%284x%5E2-9%29 Notice that these two factors are the difference of squares. The difference of squares can be factored thus:
A%5E2-B%5E2+=+%28A-B%29%28A%2BB%29 So, applying this to your result, we get:
%284x%5E2-1%29%284x%5E2-9%29+=+%282x-1%29%282x%2B1%29%282x-3%29%282x%2B3%29