Maths!!!

展開吧
-3 (2d+e) (e-2d)
=-3 (2de-4d²+e²-2de)
=-3 (e²-4d²)
=-3e²+12d²
=12d²-3e²........完成

仲有簡單d
-3 (2d+e) (e-2d)
=3 (2d+e) (2d-e) .............a-b=-(b-a)
=3[(2d)²-(e)²].............(a+b)(a-b)=a²-b²
=3(4d²-e²)
=12d²-3e².......完成

-3 (2d+e) (e-2d)
= -(6d+3e)(e-2d)
= -(6de-12d^2+3e^2-6de)
= -(3e^2-12d^2)
= 12d^2-3e^2