If (x+3)(x+3)(x+3) is a factor of P(x)=x2+kx−6P(x) = x^2 + kx - 6P(x)=x2+kx−6, what is kkk?
k=1k = 1k=1
k=−1k = -1k=−1
k=5k = 5k=5
k=−5k = -5k=−5