Which of the following expressions cannot be factored?

[dododa life is good:)]

Which of the following expressions cannot be factored into a product of lower degree terms over the set of real numbers?

f8a3 + b3
g4x2 - 12xy + 9y2
hx2 + 5x + 25
j16a2 - 9b2

 

[DEE W]

x^2 + 5x + 25

 

[Kurumi]

f) 8a^3 + b^3 can't be factored.