NCERT Class 12 · Ch 10 Exercise 10.3 · Q7
NCERT Class 12 Maths · Chapter 10 Vector Algebra · Exercise 10.3 Question 7
Expand (3a−5b)·(2a+7b).
💡 Concept Hints
- Write the vector components and identify the required direction or geometric relation.
- Use the magnitude, dot-product, cross-product or section formula that matches the requested quantity.
✅ Step-by-Step Solution
Final Answer: 6|a|²+11a·b−35|b|².
- Distribute to obtain 6a·a+21a·b−10b·a−35b·b.
- Use symmetry a·b=b·a and a·a=|a|²; combine the middle coefficients to get 11.
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