Well, I am only currently doing 2U, but I do have to say one thing; don't let that exam get to your head!
Compare it to your previous exams that year, how did you go then? What was the grade average for this exam? Do you understand the content? Was the reason for not doing well because of your lack of knowledge, or nervousness, or silly/habitual errors?...
I knew some people that essentially failed to slightly passed their 3U exams, and now they are doing really well. One example is this YouTuber called Nick, from ThatStudentLife, he failed his first three 3U exams in year 11. Now, his ATAR is 97.5 or somewhere around that while mentioning he did good in 3U.
Just learn from your mistakes, go through the content (maybe redo the test?), and just be confident.
I did quite crap in my first 2U exam (not a fail, but a bloody 67% for Algebra and Linear, how the hell...) but I knew it wasn't because I lacked knowledge, but rather habitual errors and my lack of revision.
I now am at a course average of 82%, obviously I could do much better, but I didn't let that first exam get to me despite how humiliating it was personally
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That's just my 2 cents, hope everyone does well for next term and I hope this helped you out!