SOLUTION: I don't quite understand this one. Find a value for k so that 9m^2 - kn^2 will have the factors 3m + 7n, and 3m - 7n. Thanks

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: I don't quite understand this one. Find a value for k so that 9m^2 - kn^2 will have the factors 3m + 7n, and 3m - 7n. Thanks      Log On


   

Question 41165: I don't quite understand this one.
Find a value for k so that 9m^2 - kn^2 will have the factors 3m + 7n, and 3m - 7n.
Thanks
Answer by vidhyak(98) About Me  (Show Source):
You can put this solution on YOUR website!
Find a value for k so that 9m^2 - kn^2 will have the factors 3m + 7n, and 3m - 7n.


(a + b)(a-b) = a^2 - b^2
The factors are 3m + 7n, and 3m - 7n. Let's apply the above formula
a = 3m and b = 7n

(3m + 7n)(3m - 7n) = 9m^2 - 49n^2

Comparing 9m^2 - 49n^2 with 9m^2 - kn^2, we get k = 49