(s-2t)(-s-2t)-(s-2t)²=什么?

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(s-2t)(-s-2t)-(s-2t)²=什么?(s-2t)(-s-2t)-(s-2t)²=什么?(s-2t)(-s-2t)-(s-2t)²=什么?(s-2t)(-s-

(s-2t)(-s-2t)-(s-2t)²=什么?
(s-2t)(-s-2t)-(s-2t)²=什么?

(s-2t)(-s-2t)-(s-2t)²=什么?
(s-2t)(-s-2t)-(s-2t)²
=-(s-2t)(s+2t)-(s-2t)²
=-s²+4t²-s²+4st-4t²
=-(2s²-4st)
=2s(2t-s)

(s-2t)(-s-2t)-(s-2t)²
=-(s-2t)(s+2t)-(s-2t)²
=-(s-2t)[s+2t-(s-2t)]
=-4t(s-2t)