... 2). 35 . T´ınh vi phˆan cu’a h`am f(x, y)=x 3 + y 3 .´U.ng du.ng dˆe’t´ınhxˆa´pxı’(1, 02) 3 +(1, 97) 3 .(DS. ≈ 2, 95)Trong c´ac b`ai to´an sau dˆay (36 -38 ) h˜ay t´ınh vi phˆan ... 02.9 .3. Cu..c tri.cu’a h`am nhiˆe`ubiˆe´n 15721. f = xyz v´o.ic´acdiˆe`ukiˆe.n x + y + z =5,xy + yz + zx =8.(DS. fmax=4427ta.i4 3 ,4 3 ,7 3 ;4 3 ,7 3 ,4 3 ;7 3 ,4 3 ,4 3 fmin=4ta.i(2, ... 93) 2(DS. ≈ 4.998) 32 . i) a =(1.04)2,99+ln1, 02. (DS. 1,05)Chı’dˆa˜n. X´et h`am√xy+lnz.ii) b = 3 (1, 02)2+(0, 05)2.(DS. 1,0 13) Chı’dˆa˜n. X´et h`am 3 x2+ y2. 33 ....