Answer:
K<-12
Explanation:
+ For that, we need the delta negatif.
+ The delta= b^2-4ac=12^2-4(-3)(k)=144+12k<0
Then, 12k<-144 (divise both sides by 12)
we have k<-12
Or an other way:
-3x^2+12x+k=0 (divise both sides by -3)
x^2-4x-k/3=0
x^2-4x+4 -4-k/3=0
(x-2)^2=4+k/3
Now , we need 4+k/3<0, k/3<-4 or k<-12
Hope you understand.