i don't get what i'm supposed to do

Good hearing from you, Mathalina!

the left-most term is made up of 3x*x ...

the right-most term is made up of -1*1 ...

one mix is (3x-1)(x+1)= 3x^2 + 3x - x -1 = 3x^2 + 2x - 1 ==> k=2 ...

the other's (3x+1)(x-1)= 3x^2 - 3x + x -1 = 3x^2 - 2x - 1 ==> k= -2 ... Regards :)

## Comments

N.D. -- thanks for the edit, ma'am ...