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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 10: cm đẳng thức sau : ab + de – ac -db +ef = cf (vecto nhé)

Toán Lớp 10: cm đẳng thức sau :
ab + de – ac -db +ef = cf
(vecto nhé)

Comments ( 2 )

  1. $\overrightarrow{AB}+\overrightarrow{DE}+\overrightarrow{AC}+\overrightarrow{DB}+\overrightarrow{EF}=\overrightarrow{CF}$
    Ta có: $VT=\overrightarrow{AB}+\overrightarrow{DE}-\overrightarrow{AC}-\overrightarrow{DB}+\overrightarrow{EF}\\\;\ \quad =\left(\overrightarrow{AB}-\overrightarrow{DB}\right)+\left(\overrightarrow{DE}+\overrightarrow{EF}\right)-\overrightarrow{AC}\\\;\ \quad = \left(\overrightarrow{AB}+\overrightarrow{BD}\right)+\overrightarrow{DF}-\overrightarrow{AC}\\\;\ \quad =\overrightarrow{AD}+\overrightarrow{DF}+\overrightarrow{CA}\\\;\ \quad =\overrightarrow{CD}+\overrightarrow{DF}=\overrightarrow{CF}=VP$

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222-9+11+12:2*14+14 = ? ( )