Evaluate `(3veca-5vecb).(2veca+7vecb)`

Explanation

To evaluate the expression \((3\vec{a} - 5\vec{b}) \cdot (2\vec{a} + 7\vec{b})\), we will use the distributive property of the dot product.

### Step-by-Step Solution:

1. **Write the expression**:
\[ (3\vec{a} - 5\vec{b}) \cdot (2\vec{a} + 7\vec{b}) \]
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