Question

Tìm a,b,c biết:

a) \(ab=\frac{3}{4};bc=\frac{4}{5};ca=\frac{3}{4}\)

b) \(a\left(a+b+c\right)=-12;b\left(a+b+c\right)=18;c\left(a+b+c\right)=30\)

c)\(ab=c;bc=4a;ac=9b\)

Answer 1

Khan rung be 3 dang thuc ta dc

ac.bc.ca=9/25

=>(abc)^2=9/125=(3/5)^2=(-3/5)^2

=>abc=-3/5 va abc=3/5

+) voi abc=3/5,ab=3/4 ta co c=3/5 :3/4=...

+)voi abc=-3/5 thi....

B) cong tung ve 3 dthuc ta dc

a(a+b+c)+b(a+b+c)+c(a+b+c)=36

=>(a+b+c)^2=36=6^2=(-6)^2

=>a+b+c=...