请问am的过去时是was还是were?

问题描述:

请问am的过去时是was还是were?
1.He was in San Francisco last year,but I (was)in New York.
2.If I (were),I would buy a house at the seaside.
请看以上2句,为什么I后面有跟was,也有跟were?am的过去时到底是was还是were?

第二句是虚拟语气
虚拟语气中人称后都是were 这是规定
第一句就是单纯的一般过去时