Ta có :
\(\left(a-b\right)\left(c-d\right)\left(e-f\right)x=\left(b-a\right)\left(c-d\right)\left(f-e\right)\)
\(\Leftrightarrow x=\frac{\left(a-b\right)\left(c-d\right)\left(e-f\right)}{\left(b-a\right)\left(c-d\right)\left(f-e\right)}\)
\(\Leftrightarrow x=\left(-1\right)\left(-1\right)\left(-1\right)\)
<=> x = - 1
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