Question

if 5 is a root of the equation x^2- kx-10 =0 , what is the value of k?

Answer 1

If 5 is a root, then this means that x = 5 would make the entire left side equal to 0. So simply plug in x = 5 and solve for k.


x^2- kx-10 =0


(5)^2- k(5)-10 =0


25 - 5k - 10 = 0


15 - 5k = 0


-5k = -15


k = -15/(-5)


k = 3

Answer 2

( x-5)(x+2) = x^2 - 3x - 10 = 0

k = 3