Factor the Following Polynomials:

x²-81

x²-13x+36

Which polynomial is a special product and why?
I dont know how to factor. Anyone want to explain?

Question

Factor the Following Polynomials:

x²-81

x²-13x+36

Which polynomial is a special product and why?
I dont know how to factor. Anyone want to explain?

anonymous · Answer

in english, this is the "difference to two squares"

anonymous · Answer

the difference of two squares factors as 
$$a^2-b^2=(a+b)(a-b)$$

anonymous · Answer

so would i plug into that ^^

anonymous · Answer

so the first example, we have $x^2-81$ think $a=x,b=9$

anonymous · Answer

yes, replace $a$ by  $x$ and $b$ by $9$

anonymous · Answer

$$x^2-13x+36$$ is a bit different
you have to think of two numbers whose product is $36$ and that add to $-13$ 
since they add to $-13$ they must both be negative

anonymous · Answer

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

anonymous · Answer

yes that is correct

anonymous · Answer

now for $x^2-13x+36$ since $-9\times (-3)=36$ and $-9+(-3)=-13$ it factors as $(x-9)(x-3)$
you should check that this works