How do you factor by grouping #x^3+6x^2-5x-30#?

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Answer 1 · 2015-06-08T19:03:13

#x^3+6x^2-5x-30#

#=(x^3+6x^2)-(5x+30)#

#=x^2*(x+6)-5*(x+6)#

#=(x^2-5)(x+6)#

If you allow irrational coefficients...

#=(x^2-(sqrt(5))^2)(x+6)#

#=(x-sqrt(5))(x+sqrt(5))(x+6)#

..using the difference of squares identity:

#a^2-b^2 = (a-b)(a+b)#