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In a DeltaABC, if 2AC=3CB, then 2OA+3OB ...

In a `DeltaABC`, if 2AC=3CB, then 2OA+3OB is equal to

A

5OC

B

`-OC`

C

`OC`

D

none of these

Text Solution

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The correct Answer is:
To solve the problem, we need to find the value of \(2OA + 3OB\) given that \(2AC = 3CB\) in triangle \(ABC\). ### Step-by-Step Solution: 1. **Understanding the Given Condition:** We are given that \(2AC = 3CB\). This implies a relationship between the segments \(AC\) and \(CB\). 2. **Setting Up the Triangle:** Let's denote the points of the triangle as \(A\), \(B\), and \(C\). We will also introduce a point \(O\) outside the triangle. 3. **Expressing Vectors:** We can express the vectors \(OA\) and \(OB\) in terms of \(OC\): - In triangle \(OAC\): \[ OA = OC + CA \] - In triangle \(OBC\): \[ OB = OC + CB \] 4. **Substituting into the Expression:** Now, we substitute these expressions into \(2OA + 3OB\): \[ 2OA + 3OB = 2(OC + CA) + 3(OC + CB) \] 5. **Distributing the Scalars:** Distributing the scalars gives us: \[ = 2OC + 2CA + 3OC + 3CB \] 6. **Combining Like Terms:** Now, combine the terms: \[ = (2OC + 3OC) + 2CA + 3CB = 5OC + 2CA + 3CB \] 7. **Using the Given Condition:** From the given condition \(2AC = 3CB\), we can express \(AC\) in terms of \(CB\): - Rearranging gives us \(CA = \frac{3}{2}CB\). - Therefore, substituting \(CA\) into our equation: \[ 2CA = 2 \left(\frac{3}{2}CB\right) = 3CB \] 8. **Substituting Back:** Now substitute \(2CA\) back into our expression: \[ 5OC + 3CB + 3CB = 5OC + 6CB \] 9. **Final Expression:** Since \(2AC = 3CB\), we can conclude that \(2CA + 3CB = 0\) (as they are equal in magnitude but opposite in direction). Thus: \[ 2CA + 3CB = 0 \Rightarrow 5OC + 0 = 5OC \] ### Conclusion: Thus, the final result is: \[ 2OA + 3OB = 5OC \]

To solve the problem, we need to find the value of \(2OA + 3OB\) given that \(2AC = 3CB\) in triangle \(ABC\). ### Step-by-Step Solution: 1. **Understanding the Given Condition:** We are given that \(2AC = 3CB\). This implies a relationship between the segments \(AC\) and \(CB\). 2. **Setting Up the Triangle:** ...
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