In order to factor  , first we need to ask ourselves: What two numbers multiply to -60 and add to -11? Lets find out by listing all of the possible factors of -60
Factors:
1,2,3,4,5,6,10,12,15,20,30,60,
-1,-2,-3,-4,-5,-6,-10,-12,-15,-20,-30,-60,List the negative factors as well. This will allow us to find all possible combinations
These factors pair up to multiply to -60.
(-1)*(60)=-60
(-2)*(30)=-60
(-3)*(20)=-60
(-4)*(15)=-60
(-5)*(12)=-60
(-6)*(10)=-60
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 | | | -60 | || | 1+(-60)=-59 | | 2 | | | -30 | || | 2+(-30)=-28 | | 3 | | | -20 | || | 3+(-20)=-17 | | 4 | | | -15 | || | 4+(-15)=-11 | | 5 | | | -12 | || | 5+(-12)=-7 | | 6 | | | -10 | || | 6+(-10)=-4 | | -1 | | | 60 | || | (-1)+60=59 | | -2 | | | 30 | || | (-2)+30=28 | | -3 | | | 20 | || | (-3)+20=17 | | -4 | | | 15 | || | (-4)+15=11 | | -5 | | | 12 | || | (-5)+12=7 | | -6 | | | 10 | || | (-6)+10=4 | We can see from the table that 4 and -15 add to -11.So the two numbers that multiply to -60 and add to -11 are: 4 and -15
Now we substitute these numbers into a and b of the general equation of a product of linear factors which is:
 substitute a=4 and b=-15
So the equation becomes:
(x+4)(x-15)
Notice that if we foil (x+4)(x-15) we get the quadratic again
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