Relative Velocity in Two Frames

v_{A ∣ B - x} = - v_{B ∣ A - x}

$v_(A|B-x) = - v_(B|A-x)$

(v_{B ∣ A - x}) x-Velocity of B

$(v_(B|A-x))"x-Velocity of B"$

University Physics 12th Edition, Chapter 3, Equation #3.34