For 4.25, the polynomial is $x^3 + 9x^2 + 26x + 24$.  To factor it, you can try Rational Root Theorem, and for any factor of the type $(x-a)$,  $a$ should be a factor of $24$.  Try a few factors of $24$, and as soon as you find one number that fits, you will be good shape.

For 4.29, The polynomial is $a^5 + a^4 + 1$.  your method is not bad.  Let's see where it leads:

$$1+a+a^2+a^3+a^4+a^5 = \frac{a^6-1}{a-1}=\frac{(a^3+1)(a^3-1)}{a-1}=(a^3+1)(a^2+a+1)$$

You may try to fill in the rest.