Vì: \(\left(a-b\right)\left(c-d\right)\left(e-f\right)x=\left(b-a\right)\left(d-c\right)\left(f-e\right)\)
Nên:
\(\dfrac{\left(a-b\right)\left(c-d\right)\left(e-f\right)}{\left(b-a\right)\left(d-c\right)\left(f-e\right)}=\dfrac{1}{x}\\ \Rightarrow\dfrac{-1}{1}=\dfrac{1}{x}\\ \Rightarrow\dfrac{1}{x}.1=-1\\ \Rightarrow\dfrac{1}{x}=-1\\ x=1:-1=-1\)