Possible derivation:
d/da(4 - 8 a)
Differentiate the sum term by term and factor out constants:
= d/da(4) - 8 (d/da(a))
The derivative of 4 is zero:
= -8 (d/da(a)) + 0
Simplify the expression:
= -8 (d/da(a))
The derivative of a is 1:
= -8 1
Simplify the expression:
Answer: = -8
