Find f'(a). f(t) = 2t^3 + t
\(f(t)=2t^3+t\\\\f'(t)=3\cdot2t^{3-1}+1=6t^2+1\\\\\boxed{f'(a)=6a^2+1}\)
using derivations laws f(t) = 2t^3 + tf'(t)=6t^2+1substituting a instead of tf'(a)=6a^2+1hope it helps
