Greetings from Brasil...
To solve this question, just replace X of function F(X) with A + 3
F(X) = 2X² - 4X - 3
F(A + 3) = 2 · (A + 3)² - 4 · (A + 3) - 3
(A + 3)² = A² + 2 · A · 3 + 3²
F(A + 3) = 2 · (A² + 6A + 9) - (4A + 12) - 3
F(A + 3) = 2A² + 12A + 18 - 4A - 12 - 3
F(A + 3) = 2A² + 8A + 3