Posted by Kate on .
I haven't done factoring in ages
I'm trying to factor this
X^2  2X + 8
If i remeber correctly sense the leading coefficent is 1 the factored form is in this format
(XA)(XB)
which would give you
X^2 AX  Bx + AB
or simply
X^2 (A+B)X +AB
so then in my problem
(A+B)X = 2
AB = 8
So I don't know were to go from here
What is the real way to do this? Not the way they teach you in 8 grade with the table and the gaint X but the real mathematical way to do this? Not just guess and check in your head tell you find an answer but the real way a professional person would do this? Guessing and checking takes to long?
so please tell me the REAL way to do this not just guessing and checking. I also don't know the answer to this problem...
Thanks!!!

Math 
Reiny,
If the leading coefficient is 1, then what you describe is correct
that is,
you are looking for two numbers A and B so their product is the constant at the end, and their sum is the middle coefficient.
so we are looking for two numbers whose product is +8 and their sum is 2
(there are no such rational numbers)
Are you sure the last number wasn't 8 ?
Then the two numbers would have been 4 and +2
for (x4)(x+2)
The way you typed it, there would be no factors with rational numbers.