Tìm đạo hàm riêng cấp 1 cấp 2 của hàm số: z= X³ - 2Y⁴ + 2XY - Y +1

Avideo game enthusiast saved $750 to spend on a video game player and games. the player costs $400. the games costs $49 each. at most how many games can this enthusiast buy along the player