trebuie sa calculam: a×b+2×a×c-a×d dam factor comun pe a si obtinem
a×b+2×a×c-a×d = ax(b+2c-d) = 4/9 x (b+2c-d)
stim ca:
b+c=15/8
c-d = 9/20
- adunam cele 2 relatii si obtinem:
b+2c-d = 15/8+9/20
b+2c-d = 186/80=93/40
a×b+2×a×c-a×d = ax(b+2c-d) = 4/9x93/40 = 93/90
