Question

1, Tìm a,b,c

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

Answer 1

a(a+b+c) + b(a+b+c) + c(a+b+c) = -12 + 18 + 30

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

a+b+c=6

Ta có: a(a+b+c0 = -12

a* 6 = -12

a= -2

b(a+b+c) = 18

b* 6 = 18

b=3

c(a+b+c) = 30

c*6 = 30

c=5

Answer 2

Theo đầu bài ta có:
\(\hept{\begin{cases}a\left(a+b+c\right)=-12\\b\left(a+b+c\right)=18\\c\left(a+b+c\right)=30\end{cases}}\)
\(\Rightarrow a\left(a+b+c\right)+b\left(a+b+c\right)+c\left(a+b+c\right)=-12+18+30\)
\(\Rightarrow\left(a+b+c\right)\left(a+b+c\right)=6+30\)
\(\Rightarrow\left(a+b+c\right)^2=36\)
\(\Rightarrow a+b+c=6\)
\(\Rightarrow\hept{\begin{cases}a=-2\\b=3\\c=5\end{cases}}\)

Answer 3

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

Theo bài ra , ta có : 

-12 : (a+b+c) = a

18 : (a+b+c) = b

30 : (a+b+c) = c 

=) a x -12 = (a+b+c)

   b x 18 = (a+b+c)

  c x 30 = (a+b+c)

Vậy .......................  mik bí rồi 

Answer 4

ban cold wind tra loi dung rui

Answer 5

a(a+b+c) + b(a+b+c) + c(a+b+c) = -12 + 18 + 30
(a+b+c) (a+b+c) = 36
a+b+c=6
Ta có: a(a+b+c0 = -12
a* 6 = -12
a= -2
b(a+b+c) = 18
b* 6 = 18
b=3
c(a+b+c) = 30
c*6 = 30
c=5

chúc cậu hok tốt @_@

Answer 6

Ban Cold Wind dung roi, minh cung giai theo cach do !

Answer 7

Ta có : a(a+b+c)+b(a+b+c)+c(a+b+c)=-12+18+30

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

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

=>a+b+c=+-6 mà a(a+b+c)=-12, b(a+b+c)=18, c(a+b+c)=30

=>a=-2, b=3, c=5 hoặc a=2, b=-3, c=-5

             Vậy (a,b,c) thuộc {(-2;3;5); (2;-3;-5)}

Answer 8

Ta có : a(a+b+c)+b(a+b+c)+c(a+b+c)=-12+18+30

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

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

=>a+b+c=+-6 mà a(a+b+c)=-12 ,b(a+b+c)18, c(a+b+c)=30

=>(a;b;c) thuộc {(-2;3;5);(2;-3;-5)}