Hello Vaishu,
First of all I would like to tell you that don't lose hope, if you have written exact answers of the questions you have answered then you will must pass in the exam.
Now in the case if you are not able to score pass marks in Math, then if you have given your 12th board from CBSE board , then appear for the improvement exam.
If you're from any state board, then appear for the compartmental exam.
And you must prepare well for your improvement (compartmental), and score good.
Best of luck.

Good morning,
If you're an isc student ,you might need not to give retest next year unless you didn't fail in any other subject .But if you get failed in any other subject,then you will have write exam next year .
If you're a cbse student ,you might not have to waste a year ,you will have to write the exam within this year prior to 1 month of result.
Thank you.