SOLUTION: Factor completely. x2 � 11x + 18

Question 117163: Factor completely. x2 � 11x + 18
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!

Looking at we can see that the first term is and the last term is where the coefficients are 1 and 18 respectively.

Now multiply the first coefficient 1 and the last coefficient 18 to get 18. Now what two numbers multiply to 18 and add to the middle coefficient -11? Let's list all of the factors of 18:

Factors of 18:
1,2,3,6,9,18

-1,-2,-3,-6,-9,-18 ...List the negative factors as well. This will allow us to find all possible combinations

These factors pair up and multiply to 18
1*18
2*9
3*6
(-1)*(-18)
(-2)*(-9)
(-3)*(-6)

note: remember two negative numbers multiplied together make a positive number

Now which of these pairs add to -11? Lets make a table of all of the pairs of factors we multiplied and see which two numbers add to -11

First Number	Second Number	Sum
1	18	1+18=19
2	9	2+9=11
3	6	3+6=9
-1	-18	-1+(-18)=-19
-2	-9	-2+(-9)=-11
-3	-6	-3+(-6)=-9

From this list we can see that -2 and -9 add up to -11 and multiply to 18

Now looking at the expression , replace with (notice adds up to . So it is equivalent to )

Now let's factor by grouping:

Group like terms

Factor out the GCF of out of the first group. Factor out the GCF of out of the second group

Since we have a common term of , we can combine like terms

So factors to

So this also means that factors to (since is equivalent to )

-------------------------------
Answer:

So factors to
RELATED QUESTIONS
Factor completely. x2 � 3x � 18 (answered by corrie21)

Factor completely. x2 � 3x �... (answered by checkley71)

13. Factor completely. x2 � 3x � 18 (answered by adamchapman)

x2+11x+18=0 (answered by Alan3354)

Factor completely. x2 - 50xy... (answered by richwmiller)

Factor completely. x^2 � 11x + 18 i entered it wrong the first time,... (answered by jim_thompson5910)

Factor completely: x2 � 9x + 20 (answered by wuwei96815)

Factor completely: x2 � 9x + 20 (answered by checkley77)

Factor completely: x2 � 9x + 20 (answered by nerdybill)