ri rru ruyBx srxn r,op to rgpr so GrAo DUC vA DAo rAo HA NOI Biit NAU ugc 2ot9 -2020 M6n thi : TOAN Ngdy thi : 02 thdng ndm 2019 Thdi gian ldm bii : 120 philt (2 J".r) Cho hai 25-x l) Tinh gi6 tri cria bi6u t vitB= 15-J; -T= _ r -25 vu+t) thric ,4 o = 2) Rrit gqn bi6u thric B 3) Tim t6t BnifiQ,5 ci Vz + vo,r>0,r+25 -T=1 !u - b -+ gi6 tri nguyCn cria o d6 biAu thrlc P = A.B dgt gi6 tri nguyOn lon nhdt diiim) Gidi bai bdn sau bing cdch lQp phtrong tinh ho\c hQ phtrong trinh : Hai dOi cdng nh6n cirng ldm chung mQt c6ng viQc thi sau 15 ngdy lim xong Ni5u ttQi thri , nhAt lim ri6ng rdi drmg lai vi 0 2) Vm cit (P) tai hai di0m phan birlt vrii moi gi6 tri cua rn b) Tim tat ce gi{ tri cta m d c (d) cIt (P) tai hai.li c m phin bift Vay (,1) hoinh 'll :r thiia Theo dinh ly Vi-et: J' rt 11 mi n+=+ TT + 12 = 2rn vd '+I:DK: J, 0,2 1u6n aI6 :r tla 0,2 e tt -2m^r+m'-l=O r,J', 0,5 r rr" r,r, r{ /Oatnt'l c6 =m -1 # :dG via \ _T I J -2+ rl t,*,,= -2+.r,r, -I rrx, rrr, -=e 2m = -2+ m' -t p> l1 GTLN cua P =2l.xity rakhi a = 6.r, - toa u=-Ji, GTNNcua P=1, xriyrakhi a=b=1 a = b = -1 ro\(; t)t[.\l n r 0,2 t I l 10,0 u 'cl; ,l ... !=40 D o i chi6u clidu ki6n vd k€t luAn: d6i thir nhdt I im ri6ng thi sau 24 ngdy xong vi c cl i thu hai lim ri6 thi sau 10 n a xon c oll VICC NI6t b n nu'6c inox c6 d4ng m6t hinh trg v6i chi u cao... ; ia* ii' ;8ir .; ; aii o:25 Goi thoi gian ddi thu hai ldm ri6ng xong c6ng vi6c ld y (d 0) o )5 cqi ihoi gian doi tnu nhdt ti,r, rieng xong.ong Bii II ) "ie 1) I ngAy dQi rhu... hai lirm dutvc ] :t I tcong uiect n )1 (c6ng viec) v Hai d6i ctng lim chung mQt c6ng vi6c sau 15 ngdy xong c6 phuong trinh L 1tt = (l) -+ r 1! 15 n ) t lim ri6ng vi d6i thu hai ld m tlep cong vrec