... f, ϕ) − ψδT 2 L 2 (Ω)− u(., T ; fN, ϕ) − ψδT 2 L 2 (Ω)= u(., T ; f, ϕ) − u(., T; fN, ϕ) + u(., T ; fN, ϕ) − ψδT 2 L 2 (Ω)− u(., T ; fN, ϕ) − ψδT 2 L 2 (Ω)= u(., ... fN, ϕ) 2 L 2 (Ω)+ 2( u(., T ; f, ϕ) − u(., T ; fN, ϕ), u(., T ; fN, ϕ) − ψδT)= u(., T ; f − fN, 0) 2 L 2 (Ω)+ 2( u(., T ; f − fN, 0), u(., T ; fN, ϕ) − ψδT)fN→ f L 2 (Ω), ... (2. 1)(uNt, ψl) +ni=1(nj=1aijuNxj+ aiuN, ψlxi) +ni=1(biuNxi+ auN, ψl) = (fN, ψl); l = 1, 2, , N. (2. 2)uNl(0) = (ϕ, ψl); l = 1, 2, , N, (2. 3)L 2 (Ω)...