which polynomial can not be factor

Question

Circle any polynomials below that cannot be factored any further using integers.
1)  x²– 100  

           

2) 125x³+ 1

                 

3) 6y²– 6y + 1

         

4- x²– 20

Answer 1

You can see that (1) is a difference of perfect squares, and (2) is a sum of perfect cubes, both of which may be factored using integers.  Note (3) requires use of the quadratic formula, while (4) is not a difference of perfect squares.  The answer is (3) and (4).