Question

Find the value of k for which the equation has equal roots x^2+(k+9)x+15=0 ​

Answer 1

k=-9±2√15

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