Question

Ajutor!!!! 226 227 si 228 nu is foarte grele, dar mai am de facut inca 15 ex pana la ora 12.... Ajutatima varog

Answer 1

226.     (1,2,3) , (1,2,4), (1,2,5), (2,3,4), (2,4,5), (3,4,5)
227. A(6,2),  B(2m-1,2), C(7,2)       (2m-1+ 6)/2 = 7   2m + 5 = 14   m = 11/2
228. AB = 6   AC = 8   BC = 12
se construieste un Δ oarecare ABC ; se construieste  AD⊥BC;
in ΔADC  AD² = AC² - CD²
in ΔADB  AD² + AB² - BD² ⇒   AC² - CD² = AB² -BD²  
AC² - AB² = (CD-BD)(CD+BD)    64 - 36 = 12(CD-BD) 
CD-BD = 7/3
CD +BD = 12       2CD = 7/3+12 = 43/12    CD = 43/24 
 cosC = DC/BC = 43/(24·12) = 0,1493