One solution to the problem below is 10. what is the other solution? problem:b^2-100=0

Which one ? is the answer and how to find this answer

Evaluate cos2θ for cosθ = square root of 3/2

Nick has box brads. he uses 4 brads for the first project. nick let’s b represent the original number of brads and finds that for the second project, the number of brads he uses is 8 more than half the difference of b and 4. write an expression to represent the number of brads he uses for the second project.