What are the zeros of $x^2-9$ ?

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Answer 1 · 2017-04-16T13:24:33

$x=3$ and $x=-3$

The difference of squares identity can be written:

$a^2-b^2=(a-b)(a+b)$

Note that both $x^2$ and $9=3^2$ are perfect squares, so we find:

$x^2-9 = x^2-3^2 = (x-3)(x+3)$

So the zeros are $3$ and $-3$

What are the zeros of x^2-9x^2-9 ?