👤

  Daca a+b=20si b+c=30,calculati 3xa+7xb+4xc

Răspuns :

a+b=20
b+c=30

=>3*a+7*b+4*c=
=3*a+3*b+4*b+4*c=
=3*(a+b)+4*(b+c)=
=3*20+4*30=
=60+120=
=180
3xa+7xb+4xc
3a+3b+4b+4c=
3(a+b)+4 (b+c)=
3*20+4*30 = 
60+120=180