Step-by-step explanation:
F(x) = ∫ₐˣ t⁷ dt
F(x) is the area under f(t) between t=a and t=x. When x=a, the width of the interval is 0, so the area is zero.
F(6) = 0, so a = 6.
F(x) = ∫₆ˣ t⁷ dt
F(6) = ∫₆⁶ t⁷ dt
F(6) = 0