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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