How do you write $9x^2 – 64$ in factored form?

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Answer 1 · 2018-04-10T20:54:29

$(3x+8)(3x-8)$

Difference of two squares (DOTS: $a^2-b^2=(a-b)(a+b)$ ) comes in handy with these sorts of equations

Answer 2 · 2018-04-10T20:56:59

You may see that 9 and 64 are both squares.

Now we may rewrite as:

$=3^2x^2-8^2=(3x)^2-8^2$

And the difference of two squares $A^2-B^2=(A+B)(A-B)$

Or, in this case where A=3x and B=8:

$=(3x+8)(3x-8)$

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