I need help with this precalculus problem?

Question

if f(x) = -2x^2 + 6x + k and f(0)= -1, find k?

I want to know HOW it's done and WHY you do what you do in the problem. In other words, explain what you did.

Best answer gets 10 points.

Answer 1

if f(x) = -2x^2 + 6x + k and f(0)= -1, find k?
f(0) = -2(0)^2 +6(0) +k = -1
0+0+k = -1
k = -1

Answer 2

substitute x = 0 in the function f(x) = -2x^2 + 6x + k , you get f(0)= -2(0)^2 +6 (0)+k = k
f(0)= k
you were given f(0) =-1 , from these two equations you get k =-1