Multiply the 30 by the -20, getting -600
Write down all the products of two integers which gives 600
600*1
300*2
100*3
150*4
120*5
100*6
75*8
60*10
50*12
40*15
30*20
25*24
Now out beside all those write their difference,
since -600 is negative. (If it had been positive
we would have found ther sum)
600*1 600-1 = 599
300*2 300-2 = 298
100*3 100-3 = 97
150*4 150-4 = 146
120*5 120-5 = 115
100*6 100-6 = 94
75*8 75-8 = 67
60*10 60-10 = 50
50*12 50-12 = 38
40*15 40-15 = 25
30*20 30-20 = 10
25*24 25-24 = 1
Notice that the coefficient of the middle term, 17,
in absolute value, does not appear in the column of
differences above. Therefore the trinomial does not factor.
Edwin
