Each fundamental operation (such as adding two numbers) comes with a cost. To speed up your solution you should try to reduce the number of operations. That means looking for alterative approaches instead of just translating the math formula into code.

I'd suggest googling "Code complexity" or "Big O notation". There are tons of youtube videos on the matter as well. I would publish a youtube link here, but I doubt it's allowed.

Please use spoiler flag next time.