Evaluate the following intergrals

$I_1={\displaystyle \underset{-}{\overset{}{}}}{e}^{-2x}(x-1)dx$

$I_2={\displaystyle \underset{-}{\overset{t}{}}}{e}^{2(t-x)}(x-1)dx$

$I_3={\displaystyle \underset{-}{\overset{t}{}}}(x+1)dx-{\displaystyle \underset{-}{\overset{t}{}}}(x-1)dx$

$I_4={\displaystyle \underset{-}{\overset{t}{}}}(-x+1)dx+{\displaystyle \underset{-}{\overset{t}{}}}(x-1)dx$