Answer:
k=-9±2√15
Step-by-step explanation:
For the above quadratic to have equal roots then it's discriminant b²-4ac must equal 0
By comparing x²+(k+9)x+15=0 with ax²+bx+c=0,a=1,b=k+9 and c=15
(k+9)²-4(1×15)=0
k²+18k+81-60=0
k²+18k+21=0(factorize)
k=-9±2√15
