how do we integrate between points 3 to -1 is it possible

yes,its possible to integrate between 3 to -1.For example integration of x+5 is [xsquare/2+5x]between 3 to -1 is   [-1*-1/2+5*-1]-[3*3/2+5*3]=-24.As area will never be negative we have to take modulus of integration.Therefore answer is 24.