Answer:
k = 4
Step-by-step explanation:
In order for the claim to be true, (x-3) must be a factor of each of the terms in the first expression. That is, you must have that expression factor as ...
(x -3)(2x +5) +(x -3)(x +7)
Factoring out (x -3), we get ...
= (x -3)(2x +5 +x +7) = (x -3)(3x +12)
= 3(x -3)(x +4)
The value of k must be 4.
