mathematics is necesssary in class 10 for b.tech.
See you need to have such a combination in your class 10 such that you get the Physics, Chemistry and Mathematics in your 10+2 as it is needed if you want to study the BTech course.
I would recommend you that you must take Mathematics and Sciences of your 10th very sincerely as it will create a foundation stone laterwards.
To know more about BTech as a career visit the link below:
https://www.careers360.com/courses/b-tech-bachelor-of-technology
I hope this answer helps. All the very best for your future endeavors!