Let f(x) be the function 6x^2 - 6x +12. Then the quotient [ f(5+h)-f(5) ]/ h can be simplified to ah + b for:
a=
b=
6(5+h)^2 - 6(5+h) + 12 - (6*5^2-6*5+12)
= 6(25+10h+h^2) - 6(5+h) - 150+30
= 150+60h+6h^2-30-6h-150+30
= 60h+6h^2
now divide by h