Find dot products and perpendicular vectors

Multiply matching components and add. Perpendicular vectors have dot product 0.

1. Find the dot product ⟨5, 4⟩ · ⟨−4, 1⟩.
2. Find the dot product ⟨4, −5⟩ · ⟨−4, 3⟩.
3. Find the dot product ⟨1, −3⟩ · ⟨4, 5⟩.
4. Find the dot product ⟨−4, −1⟩ · ⟨2, 2⟩.
5. Find the dot product ⟨1, 9⟩ · ⟨−4, −9⟩.
6. Find the dot product ⟨−1, 7⟩ · ⟨−7, 7⟩.
7. Find the dot product ⟨2, 6⟩ · ⟨−4, 9⟩.
8. Find the dot product ⟨5, 4⟩ · ⟨−6, −7⟩.
9. Find the dot product ⟨−3, −5, 1⟩ · ⟨1, −2, −4⟩.
10. Find the dot product ⟨−3, −4, −6⟩ · ⟨6, −3, 6⟩.
11. Find the dot product ⟨−4, −3, −1⟩ · ⟨−2, 6, −5⟩.
12. Find the dot product ⟨−5, −4, 1⟩ · ⟨−2, −1, 3⟩.
13. For what value of k are ⟨3, 3⟩ and ⟨k, −1⟩ perpendicular?
14. For what value of k are ⟨−4, 4⟩ and ⟨k, −2⟩ perpendicular?
15. For what value of k are ⟨3, −3⟩ and ⟨k, −5⟩ perpendicular?
16. For what value of k are ⟨5, 10⟩ and ⟨k, 4⟩ perpendicular?
17. For what value of k are ⟨9, −9⟩ and ⟨k, 9⟩ perpendicular?
18. For what value of k are ⟨7, 14⟩ and ⟨k, −5⟩ perpendicular?
19. For what value of k are ⟨−5, −10⟩ and ⟨k, −7⟩ perpendicular?
20. For what value of k are ⟨8, −32⟩ and ⟨k, −5⟩ perpendicular?