Question

Tính B=(x+y)(y+z)(x+z)

Biết xyz=2, x+y+z=0

~~~FIGHTING~~~

Answer 1

 

Ta có : x+y+z=0

=>x+y=−z

y+z=−x

x+z=−y

=> B=(x+y)(y+z)(x+z)=(−x)(−y)(−z)=−xyz=−2

 

Answer 2

Ta có x+y+z=0

\(\Rightarrow x+y=-z\)

\(\Rightarrow x+z=-y\)

\(\Rightarrow y+z=-x\)

Thay vào B ta được B=\(-x.-y.-z=-\left(xyz\right)\)

mà xyz=2 \(\Rightarrow B=-2\)