Answer:
a + 7
Step-by-step explanation:
x^2 + 2x - 8. on [5,a]
(f(a)-f(5))/( a - 5 )
(( a^2 + 2a - 8 ) - 27 ) / a - 5
( a^2 + 2a - 35 ) / a - 5
(a - 5)(a + 7) / a - 5
