[3X-450]*[2X+450]=3X+2X-22500

不对.
[3X-450]*[2X+450]
=6X^2+(3*450-2*450)X-450^2
=6X^2+450X-22500
.看不懂，是解方程喔。我以为是化简呢。解方程接着来：[3X-450]*[2X+450]=6X^2+(3*450-2*450)X-450^2=6X^2+450X-202500 [3X-450]*[2X+450]=3X+2X-225006X^2+450X-202500=3X+2X-225006X^2+455x-180000=0你再接着化简就可以了。