Multiply the coefficient of the first term by the constant   1 • -31 = -31 
Find two factors of  -31  whose sum equals the coefficient of the middle term, which is   -2 .
     	-31	   +   	1	   =   	-30	
     	-1	   +   	31	   =   	30	
Observation : No two such factors can be found !!
Conclusion : Trinomial can not be factored