In order to factor  , first we need to ask ourselves: What two numbers multiply to -5 and add to -4? Lets find out by listing all of the possible factors of -5
Factors:
1,5,
-1,-5,List the negative factors as well. This will allow us to find all possible combinations
These factors pair up to multiply to -5.
(-1)*(5)=-5
Now which of these pairs add to -4? Lets make a table of all of the pairs of factors we multiplied and see which two numbers add to -4
| First Number | | | Second Number | | | Sum | | 1 | | | -5 | || | 1+(-5)=-4 | | -1 | | | 5 | || | (-1)+5=4 | We can see from the table that 1 and -5 add to -4.So the two numbers that multiply to -5 and add to -4 are: 1 and -5
Now we substitute these numbers into a and b of the general equation of a product of linear factors which is:
 substitute a=1 and b=-5
So the equation becomes:
(x+1)(x-5)
Notice that if we foil (x+1)(x-5) we get the quadratic again
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