CE = CF = 5x
AF = AD = 4
P = BE + BD + CE + CF + AF + AD
36 = 14x + 8
36 – 8 = 14x
x = 28 : 14 = 2
AB = 8 см.
(m+n)(2m-n)=2m^2+mn-n^2=2*25-36+5*6*cos120=50-36-30*sin30=-1