Question

Bài 1: Tìm a,b,c:

a, a.b=35 ;b.c=45 ;c.a=34

b, a.(a+b+c)= -12

b.(a+b+c)= 18

c.(a+b+c)= 30

c, a.b=c; b.c= 4a; a.c= 9b