having trouble on the last two

Let f(x) = 3x2 - 7x + 9. Simplify each of the following expressions. f(a ) = 30- - 7a+ 9 f (a + h ) = 3a- + 6ah+ 3h- - 7a -Th+9 F(a + h ) - f ( a ) = Gah + h- - Th (Make sure to expand and combine like terms.) X f ( a + h ) - f ( a ) = 6ath - 7 ( Make sure to cancel out the factor of h in the denominator.) C X