Question 451555
well, you know that f(2)=0, so let's find f(2) by actually plugging x=2 in the given function f(x)=3x^2+kx-4.
f(2)=3(2^2)+k(2)-4=8+2k
remember that f(2)=0, so we need to set 8+2k equal to 0 since they are both the same f(2)

8+2k=0
2k=-8
k=-4