Question

Tính -5x/21+-5y/21+-5z/21 biết x+y=-z

Answer 1

x + y = -z => x+y +z = -z + z =0

\(\frac{-5x}{21}+\frac{-5y}{21}+\frac{-5z}{21}=\frac{\left(-5x\right)+\left(-5y\right)+\left(-5z\right)}{21}=\frac{-5.\left(x+y+z\right)}{21}.\frac{-5.0}{21}=\frac{0}{21}=0\)

 

Answer 2

-5x/21+-5y/21+-5z/21=-5/21

(x+y+z)=-5/21.(-z+z)=0