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ngocphuong23


Cho $\dfrac{1}{c} = \dfrac{1}{2} . (\dfrac{1}{a} + \dfrac{1}{b})$
Biết a,b,c $\ne$ 0; b $\ne$ c
CM: $\dfrac{a}{b} = \dfrac{a - c}{c - b}$
Biết a,b,c $\ne$ 0; b $\ne$ c
CM: $\dfrac{a}{b} = \dfrac{a - c}{c - b}$