<s>[INST] Solve $(x^2 + 5)^2 - 15(x^2 + 5) + 54 = 0$ I got the square root of 14 and 11 but the answer book states that these answers are wrong. Can someone help me? I used this formula to find the individual roots 
$x = -\frac{p}{2} \pm \sqrt{(\frac{p}{2})^2 - q}$ 
 [/INST] Using middle term factor,  $$(x^2+5)^2-(9+6)(x^2+5)+6\cdot9=0$$
$$\implies (x^2+5)(x^2+5-9)-6(x^2+5-9)=0$$
$$\implies (x^2-4)(x^2-1)=0$$
$\implies x^2-1=0$ or $x^2-4=0$
Alternatively, using quadratic equation formula  for $x^2+5=\frac{15\pm\sqrt{15^2-4\cdot1\cdot 54}}{2\cdot1}=\frac{15\pm 3}2=9$ or $6$
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