只需兩個(gè)函數(shù)

和

實(shí)例網(wǎng)站：

https://www.desmos.com/calculator/0wquiujmpf?lang=zh-CN

https://www.desmos.com/calculator/s6ay58d2qh?lang=zh-CN

https://www.desmos.com/calculator/ghkvd4ybtv?lang=en