Question

a+d=17
b+c=19
Sa se afle numarul care este egal cu:
a*b+a*c+b*d+c*d

Answer 1

a+d=17
b+c=19
a*b+a*c+b*d+c*d=
=a*(b+c)+d*(b+c)=
=19a+19d=
=19*(a+d)=
=19*17=323