This can help you
a) since it is discrete we need to think about the sum thing
it it was continuous we would look at an integral thing
so I think if I remember correctly we need to find c such that
<span><span>∑<span>i=0</span>3</span>c(<span>x2</span>+4)=1
b) </span>
problem b is a similar setup
16 - -15 = 31 (negative - negative = positive)
hope this helps! :)