By the fundamental theorem of calculus,
f(x) = f (0) + ∫₀ˣ f '(t) dt
We're given that the plot of f(x) passes through the point (0, -7), so f (0) = -7, and
f(x) = -7 + ∫₀ˣ (9t ² + 4t - 4) dt
f(x) = -7 + (3t ³ + 2t ² - 4t )|₀ˣ
f(x) = -7 + (3x ³ + 2x ² - 4x)
f(x) = 3x ³ + 2x ² - 4x - 7