f(x) = ∫(1,x) f(t)/t dt + (x - 1)e^x
f'(x) = f(x)/x * dx/dx + e^x * (1 - 0) + (x - 1) * e^x
f'(x) = f(x)/x + xe^x
==> y' = y/x + xe^x
==> y' - y/x = xe^x、e^(∫ - 1/x dx) = e^(- lnx) = 1/x、将1/x乘以方程的两边.
==> y'/x - y/x² = e^x
==> (y/x)' = e^x
==> y/x = C + e^x
==> y = Cx + xe^x
f(x) = Cx + xe^x
令x = 1、f(1) = 0 ==> 0 = C + e ==> C = - e
所以f(x) = xe^x - e * x