Find a solution of the second-order IVP question (First chapter in my Diff Eq's book)

Hey all. I have this problem:

I am supposed to use this to find out what and are:

What happens when I use the first equation is I get

leaving me know way to solve for them. The answer in the back of the book says:

Can anyone show me what I should do? If this one is answered, I will be able to complete all the other problems. Because I'm getting stuck on the same thing, having 1 equation and 2 variables and

Thanks,

DHS1