Maybe a silly doubt but important

https://preview.redd.it/u8gnkw8otr6e1.png?width=808&format=png&auto=webp&s=d8b39d7cd87601d75272ce6f5424e7930a587a16 isme change in velocity nikalne me calculation kaise kiya hai in hone jisse u\^2 add hua ? on last 3 lines