CAu do 1. DU LICH
Do cludng di khong duoc l[p lai non chi c5 thd di 2
chAng dudng s6t noi tr) He NOi ddn 2 dO thi vbng trong,
cdn lai 4 chlng dudng s6t Phu L! - Nam Dinh, Hai Duong - Hii Phdng, Bic Ninh - B6c Giang, Vrnh YOn -
ViOt Tri lh bit buoc phAi qua. Nhu vAy nhidu nhat 1I qua 6 chAng dudng sat.
Vdi ki hi6u + chi dudng bQ, = chi duong sat, c6 4 lo
trinh sau : 1) HN = HD = FIP -+ BG = BN -+ TN + BK -> VT = VY -+ HD -+ HB + ND + PL = HN (sod0) 2) HN = HD = HP + ND = PL -+ HD -+ HB -> VT = VY -+ TN -+ BK -+ BG = BN = HN. 3) HN = TN + BK -+ VT = VY + FID -+ FIB -+ ND = PL -+ HD = I]P + BG + BN = HN 4) ffN =TN -+ BK -+ BG = BN -+ HD = F{P-+ ND =PL-+ FID + F{B + V'l'= \-\'- iN. M6i IO trinh tr€n lai cho tuong rlng v6i mOt lO trinh theo thri tu nguoc lai, do vAy' c5 tii ca S 1o trurh.
CAu rlo 2. BOC HOP TANG PHAITA
Dien tich 6 mar hinh vuOng cria hinh lAp phuong canh zr ld.6a2. MAnh giay hrnh ch[ nhit vdi chrdu
rdng x, chidu clii 3x c5 dion tich li 3.1. Tt 3l = 6a2 c6 x = aJ7. nghia la chreLr Long rrilnh gial'
bang <ludng ch6o hinh vuong. Cit giay thdnh 2 miinh nhu o c6ch t hoac cdch 2 trang 20.
Tir c6ch I c5 thd suy ra nhidu kidu kh6c, ching han:'cat theo dudng E(D,B)(A"C')F holc B'(D,B)(A',C1A... TiI cdchZ c6 th<i chon didm D di chuydn tiry y trong khoang Etr.
(Xent riifu trong 20)
Isinr:ioffio-soiiChi so : l2Sda :