Billy has 3,618 cards
201 * 18 = 3,618
18 card per package
201 packages
3,618 cards all together
Use the power rule
d(x^n)/dx = n·x^(n-1)
to form the derivative.
f'(x) = 4·2x -4
f'(x) = 8x - 4
Now, substitute "a" for "x" to find f'(a):
f'(a) = 8a - 4
That would be 5/8
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