1. When I was walking down the street, I slipped on a banana peel and fell on the ground. Thankfully I was alright.2. When I in school I tripped on the stairs and fell on the staircase.
 slip on something trip on somethingslip 比較有滑跤的感覺，用在被香蕉皮滑倒很貼切，而 trip 指碰到東西而跌跤。通常後面會加 fall 表示倒下的動作。
I have been wrecking my brai on this tough math question but I still cannot solve it.