Question

AB+AC+AD+EA+FA=4AB .prove it by vector method
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Answer 1

Answer:

assume you mistyped the problem, it meant: ab+ac+ad+ea+fa=4ab where each quantity is a VECTOR.

first, note AB+BC=AC and

AD=AB+BC+CD and

EA (note direction, from E to A)=-(AB+BC+CD+DE) and

FA=-(EF+AE)