先化简再求值:(2a-3b)²-(a-b)(a+4b)-3(a+b)²;其中a=1/3,b=1/2(过程)
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先化简再求值:(2a-3b)²-(a-b)(a+4b)-3(a+b)²;其中a=1/3,b=1/2(过程)
先化简再求值:(2a-3b)²-(a-b)(a+4b)-3(a+b)²;其中a=1/3,b=1/2(过程)
先化简再求值:(2a-3b)²-(a-b)(a+4b)-3(a+b)²;其中a=1/3,b=1/2(过程)
原式=(4a^2-12ab+9b^2)-(a^2+3ab-4b^2)-3(a^2+2ab+b^2)
=10b^2-21ab
=10/4-21/6
=-1