The idea is to pair up the terms, factor each sub-group, and then pull out the overall GCF to fully factor.
x^3+5x^2-6x-30
(x^3+5x^2)+(-6x-30)
x^2(x+5)+(-6x-30)
x^2(x+5)-6(x+5)
(x^2-6)(x+5)
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Answer: (x^2-6)(x+5)
