(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

If a and b are perpendicular, simplify [tex](a - 2b) \cdot (3a + 5b)[/tex]

3. The attempt at a solution

Not really sure what they're asking, but to be perp. the angle between them is 90. So using the scalar

so a.b = 0??

The answer in the book it (3a² - 10b²) and I can see that they just multiplied the as and bs together, but why?

Thanks

Thomas

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# Homework Help: Perpendicular Vectors

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