Vector PB+ vector PC

=2 vector PD

Vector PA+ vector PB+ vector PC=0

∴ vector PA+2 vector PD

=0

Vector PA=-2 vector PD

∴ vector AP=2/3 vector AD

Vector AB+ vector AC

=2 vector advertisement

=2*3/2 vector AP

=3 vector AP

= λ vector AP

∴λ=3

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