if -3 is a root of the equation x^2+(13+k)x+k=0...

1)x^2+(13+k)x+k=0
(-3)^2+-3(13+k)+k=0
-2k=30
k=-15
2)x^2+(13+-(15))x-15=0
x^2-2x-15=0
(x-5)(x+3)=0
x=5
The other root of the equation is 5

Let a be another root of the equation
Sum of roots = a - 3 = -(13+k)
Product of roots = k = -3a

Solving these two equations,
we have a - 3 = -13+3a
which gives a=5

Putting this into k=-3a, we have k = -15

a)
(-3)^2+(13+k)(-3)+k=0
k=-15
b)
x^2-2x-15=0
x=5 or x=-3
So the other root is x=5