Question 47747
Factor completely:
{{{x^2-16x+63}}}

If this expression can be factored, the factors will have the form:
{{{(x + m)(x + n)}}} where: {{{m*n = 63}}} and {{{m + n = -16)}}}
Make a list of the possibilities:
Since the sum is negative and the product is positive, both m and n must be negative.

Try: m=-3 and n=-21
m+n = -24 and m*n = 63  No good!

Try: m=-9 and m=-7
m+n = -16 and m*n = 63  This will work!

{{{x^2-16x+63 = (x-9)(x-7)}}}