2) U_t = U_xx + bU_x + f(x,t); U(0,t) = 0; U(l, t) = 0; U(x,0) = фи(x) 3) U_t = U_xx +2t + x + 6sin9x; U(0,t)=t^2; U_x(pi/2,t)=t; U(x,0) = 3sin9x 4) U_t = 9U_xx + U; U_x(0,t)=0; U_x(pi,t)=0; U(x,0)=x-3 5) U_t = U_xx + 4, -inf < x < +inf, t > 0 U(x,0) = { 8 при 0<=x<=2, 0 иначе }