How do you multiply $(9 - w) (9 + w)$ $(9-w)(9+w)$ ?

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Answer 1 · 2017-04-17T22:54:35

$81 - w^{2}$ $81-w^2$

This is something you must keep in mind: for every $a$ $a$ we have

$(a - w) (a + w) = a^{2} - a w + a w - w^{2} = a^{2} - w^{2}$ $(a-w)(a+w)=a^2- aw + aw-w^2=a^2-w^2$

In this case $a = 9$ $a=9$ so $(9 - w) (9 + w) = 9^{2} - w^{2} = 81 - w^{2}$ $(9-w)(9+w)=9^2-w^2=81-w^2$

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