I[x(t)]=∫48 [t−4x(t)]2dt,x(4)=1,x(8)=2
You need to know the form of the function x(t).
For example, you could have: x(t) = t/4 or x(t) = (t^2)/48 + 2/3 or ...
These will give different results for the integral in general.