Question 44791
Given P(x)=x^2-4x, find and simplify P(a+h)-P(a)
To get P(a+h) substitute "a+h" in place of "x", as follows:

P(a+h)=(a+h)^2-4(a+h)
      =a^2+2ah+h^2-4a-4h
To get P(a) substitute "a" in place of "x", as follows:
P(a)=a^2-4a

Now subtract P(a) from P(a+h), as follows:

P(a+h)-P(a)=2ah+h^2-4h

Cheers,
Stan H.