Originally Posted by LilDragonfly
Thus b = -8.
I do not know if you understood what topsquak said, but when you have,
It means if you integrate both sides you have,
with some constant ,
the reason to why f''(x) becomes f'(x) is because when you integrate a derivative of a function you get back the function (definition of integral). So when you have f''(x) integrating once would yield f'(x) so you need one more time:
Then use topsqaurk post to complete the problem.