Question-127566

Question Number 127566 by Ar Brandon last updated on 30/Dec/20

Answered by bramlexs22 last updated on 30/Dec/20

(\vec{a} + \vec{b}) \times (\vec{a} - \vec{b}) = \vec{a} \times \vec{a} - \vec{a} \times \vec{b} + \vec{b} \times \vec{a} - \vec{b} \times \vec{b}

[\vec{a} \times \vec{a} = 0; \vec{a} \times \vec{b} = - \vec{b} \times \vec{a}]

= 0 + 2 (\vec{b} \times \vec{a}) - 0 = 2 (\vec{b} \times \vec{a})

Commented by Ar Brandon last updated on 31/Dec/20

Thanks