Question

a,b,c sunt trei numere naturale.stiind ca a+b=7si b+c+10,calculati 3×a×b+2×c

Answer 1

b=7-a => 7-a+c=10 => c=3+a => 3ab+2c= 3a(7-a)+2(3+a)= =21a-3a^2+6+2a= (-3a^2)+23a+6