Jawapan

2015-09-22T21:18:51+08:00
= 2m^2 -mh +2mh -2h^2 -3mh +21

= 2m^2 - 2mh - 2h^2 +21
2015-09-22T21:21:44+08:00
2m²-mh+4mh-2h²-3mh+21
2m²+3mh-2h²-3mh+21
2m²-2h²+21
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