7 t-2t 2t2+2 x(t=e C+eat rt e f∫(z)dτ 1-3t+4t x(t=ec+ At e f(rdr=e-t+2r 20 ( )d t A e f    −  2 2 2 4 2 2 t t t t t   − −   = −       −    0 ( )d t At A e e f    −  2 2 2 4 1 2 2 2 t t e t t   −   =       +    0 0 ( ) ( ) ( )d A t t t At A t x t e c e e f    − − = +  0 ( ) ( )d t At At A x t e c e e f    − = +  2 2 2 1 3 4 2 2 t t t e t t t   − +   = − +        