Plugging function in a function

Hello so I have this problem that requires me to plug y(0)=0 into y=C1 I was looking into something called function handling but I'm not sure how it can be within this context can you please help me.

[VBBV]

is y = C1 a function of other variables or constant ?

[Aijalon Marsh]

y=C1 is the derivative of y=C1*x + C2