f(x) = 3x² - x + 2
f(-2) = 3 · (2)² - (2) + 2
f(-2) = 3 · 4 - 2 + 2
f(-2) = 12 - 2 + 2
f(-2) = 12
f(a + 3) = 3 · (a + 3)² - (a + 3) + 2
f(a + 3) = 3 · (a² + 6a + 9) - a - 3 + 2
f(a + 3) = 3a² + 18a + 27 - a - 3 + 2
f(a + 3) = 3a² + 17a + 26
