SOLUTION: find the value of k and the other root of 4x^2 + kx + 15=0 if 5 is one of its roots

Let  " t "  be the other root.


Then, according to Vieta's theorem,   = 5t,  which implies  t =  = .


So, the other root is  .


Next, according to Vieta's theorem  (again; this time another part of the Vieta's theorem)   = 5 +  = 5  = .


So,  k = -23.


ANSWER.  k = -23;  the other root is .