What is the dot product of a= -2i - 5j and b=i -4j

Physics

1 answer:

Dafna1 [17]3 years ago

7 0

I.i = j.j = 1
i.j = j.i = 0

(-2i - 5j)(i -4j)
= (-2i).i + (-2i).(-4j) + (-5j).i + (-5j).(-4j)
= -2 + 0 + 0 + 20 = 18

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