Question

Determine the value of k for which -3x^2+12x+k=0 has no real roots. ​

Answer 1

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.