Question

Factor the expression.

k^2 + 5kf - 50f^2

A. (k-10f)(k+5f)
B. (k+10f)(k-5f)
C. (k+10f)(k+5f)
D. (k-10f)(k-5f)

Answer 1

B. (k+10f)(k-5f) you can tell in 2 ways. 1. if the second sign is neg then the signs in the factors are going to be one neg and one positive so that knocks out C and D. Then you look at the second term and since the 5 is positive then the 10 has to be positive so you end up with a positive 5kf.

The second way is to FOIL them out. When you check B you get
`k^(2) -5kf+10kf- 50f^(2)` combine your like terms and you have your original expression of
`k^(2) +5kf-50 f^(2)`

Hope that helps