... v´o.ic´acdiˆe`ukiˆe.n x + y + z =5,xy + yz + zx =8.(DS. fmax =4 427ta.i 4 3, 4 3,73; 4 3,73, 4 3;73, 4 3, 4 3fmin=4ta.i(2, 2, 1); (2, 1, 2); (1, 2, 2))T`ım gi´a tri.l´o.n ... b`ai to´an 40 - 44 ch´u.ng minh r˘a`ng c´ac h`am d˜a cho tho’am˜an phu.o.ng tr`ınh tu.o.ng ´u.ng (gia’thiˆe´t f v`a g l`a nh˜u.ng h`am hai lˆa`nkha’ vi) 40 . u = f(x ... +∆y)22+ R2).´Ap du.ng vi phˆan dˆe’t´ınh gˆa`nd´ung (31-35)31. i) a =(0, 97)2,02(DS. ≈ 0, 94) ii) b = (4, 05)2+(2, 93)2(DS. ≈ 4. 998)32. i) a =(1. 04) 2,99+ln1, 02. (DS. 1,05)Chı’dˆa˜n....