... ta.i x ∈ M sao cho f khˆong liˆen tu.c ta.iM, t´’uc l`a t`ˆon ta.i d˜ay {xn} ⊂ M sao cho xn→ x nh’ung f(xn) f(x).Suy ra t`ˆon ta.i s´ˆo ε0> 0 sao cho ∀n, ∃nk> ... C´ac nguyˆen l´ı c’o b’an c’ua gi’ai t´ıch h`am5. Cho X, Y l`a c´ac khˆong gian ¯di.nh chu’ˆan, M ⊂ X, v`a f : M → Y sao cho f(M)compact. Ch´’ung minh n´ˆeu GA= {(x, f(x)) ... 1Ch’u’ong 2. Khˆong gian ¯di.nh chu’ˆan10. Cho A, B l`a hai to´an t’’u t´ıch phˆan trong C[a,b]v´’oi ha.ch l`ˆan l’u’o.t...