Question

Tìm số a;b;c.a+b=12;b+c=13;c+a=-15

Answer 1

ta có :

( a + b ) + ( b + c ) + ( c + a ) = 12 + 13 + ( -15 ) = 10

\(\Rightarrow\) a + b + c = 5 

+ a = ( a + b + c ) - ( b + c )  = 5 - 13 = -18

+ b =  ( a + b + c ) - ( a + c ) - 5 - ( -15 ) = 20

+ c =   ( a + b + c ) - ( a + b ) = 5 - 12 = -7

Answer 2

a+b+b+c+c+a=2a+2b+2c=2(a+b+c)=12+13+(-15)=10

=>a+b+c=5

c=5-12=-7

a=5-13=-8

b=5-(-15)=20

 

Answer 3

a=-8

b=20

c=-7

tick cho mh cho xuống -20 cái