Question

calculati:
a)ac+bc, stiind ca a+b=7 si c=10:
b)ac-bc, stiind ca a-b=14 si c=7:
c)a+c, stiind ca ab+ba=270 si b=9:
d)c, stiind ca ac-bc=120 si a-b=20.

Answer 1

a)   ac+bc = c(a+b)=10×7=70 ;
b)   ac - bc=c(a- b)=7×14=98 ;
c)   ab+bc = b(a+c) ⇔ 270=9(a+c) ⇒ a+c = 30 ;
d)   ac -bc = c(a -b) ⇔ 120=c×20   ⇒   c = 6 ;