throw good money after bad 看字面意思就很好理解，“把钱投入无底洞，花冤枉钱”。

Trying to fix that old car would just be throwing good money after bad.

试图修理那辆旧车简直就是花冤枉钱。

tear up 形容（因为情绪激动）眼里含泪（几乎要开始哭泣）。

She teared up as the award was presented to her.

给她颁奖的时候她的眼泪夺眶而出。

tear作动词还有“撕裂”的意思，tear up也表示“拆除；拆毁”。

I suggest that you tear up the composition and start over again.

我建议你把这篇作文撕掉，再从头开始写。