I need to prove that (a – b) x (a + b) = 2(a x b), where a and b are both vectors. I can’t figure out a proof.?

2 Answers

  • Ok, here’s how you do it. You know that

    (a-b)x(a+b)= axa + axb – bxa – bxb

    you know too that

    axa = 0 and bxb = 0

    you know too that

    -bxa=axb then

    (a-b)x(a+b) = axb +axb = 2(axb)

    hope this helps.

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