Question

cho a+b +c = 5; ab +bc+ca =3; tinh aa+bb+cc

Answer 1

Ý bạn là aa+bb+cc=a²+b²+c²
Ta có:
(a+b+c)²=25
<=> a²+b²+c²+2(ab+bc+ca)=25
<=> a²+b²+c²+2.3=25
<=> a²+b²+c²=19

Answer 2

cảm ơn bạn nha

Answer 3

Ta có : a+b+c = 5=>(a+b+c)²=25

Mà \(\left(a+b+c\right)^2=a^2+b^2+c^2+2\left(ab+ac+bc\right)=25\)

\(\Rightarrow a^2+b^2+c^2+6=25\)

\(\Rightarrow a^2+b^2+c^2=19\)

Vậy ..........................