SOLUTION: factor completely: x^2+9x=8

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Question 101318: factor completely:
x^2+9x=8

Answer by jim_thompson5910(28476) About Me  (Show Source):
You can put this solution on YOUR website!
x%5E2%2B9x=8 Start with the given equation

x%5E2%2B9x-8=0 Subtract 8 from both sides


Now let's factor x%5E2%2B9x-8


Solved by pluggable solver: Factoring using the AC method (Factor by Grouping)
In order to factor x%5E2%2B9%2Ax-8, first multiply the leading coefficient 1 and the last term -8 to get -8. Now we need to ask ourselves: What two numbers multiply to -8 and add to 9? Lets find out by listing all of the possible factors of -8


Factors:

1,2,4,8,

-1,-2,-4,-8, List the negative factors as well. This will allow us to find all possible combinations

These factors pair up to multiply to -8.

(-1)*(8)=-8

(-2)*(4)=-8

Now which of these pairs add to 9? Lets make a table of all of the pairs of factors we multiplied and see which two numbers add to 9

||||
First Number|Second Number|Sum
1|-8|1+(-8)=-7
2|-4|2+(-4)=-2
-1|8|(-1)+8=7
-2|4|(-2)+4=2


None of these factors add to 9. So the quadratic x%5E2%2B9%2Ax-8 cannot be factored.