Question

3a^2(a^2-4)+2a(a^2-4)-a^2+4
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Answer 1

3a²(a²-4)+2a(a²-4)-a²+4=
=3a²(a²-4)+2a(a²-4)-(a²-4)=
=(a²-4)(3a²+2a-1)=
=(a-2)(a+2)(a+1)(3a-1)

*** 3a²+2a-1=(a+1)(3a-1)
      D=2²-4*3*(-1)=4+12=16=4²
      a₁=(-2+4)/6=2/6=1/3
      a₂=(-2-4)/6=-6/6=-1
      3a²+2a-1=3(a+1)(a- 1/3)=(a+1)(3a-1)