3a方-12b方-18a-36b/4a+8b,并代入a=2012,b=-339求值
问题描述：
3a方-12b方-18a-36b/4a+8b,并代入a=2012,b=-339求值
答
3a方-12b方-18a-36b/4a+8b
=【3（a²-4b²）-18（a+2b）】/4(a+2b)
=[3(a+2b)(a-2b)-18(a+2b)]/4(a+2b)
=3/4(a+2b)-9/2
=3/4a+3/2b-9/2
=3/4x2012-3/2x339-9/2
=1059-508.5-4.5
=1059-513
=546
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