Posted by ayrajudelle on .
what is the factor of a^3  2a + 4?
please help me guys. :(

math 
MathMate,
Hint:
A cubic has to have at least one zero.
If the expression has rational factors, there would be at least one linear factor fininishing in 1,2,4 or 1,2,4, since the coefficient of a^3 is 1.
For f(a)=a^3  2a + 4
So check f(1),f(2),... and which factor is in f(a). Do a long division and try to factor the remaining quadratic. 
math 
MathMate,
Sorry, the last paragraph is not clear.
If f(a0)=0, then (xa0) is a factor of f(a). So check and see which of f(1),f(2)...=0 and hence find a rational factor of f(a).
If f(1)=0, then (a+1) is a factor.
Do a long division and factor the remaining quadratic.