How to find a vector when given its ratio with another vector?

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Can someone please explain to me how to do question 1b? Thanks!

1 Answer
Jan 5, 2018

vec(OR)=2ula-ulb

Explanation:

vec(AB)=3vec(AR)+2vec(RB)

rArrulb-ula=3(ulr-ula)+2(ulb-ulr)

rArrulb-ula=3ulr-3ula+2ulb-2ulr

rArrulr=ulb-ula+3ula-2ulb

rArrvec(OR)=ulr=2ula-ulb