xieliang414
幼苗
共回答了14个问题采纳率:100% 举报
(2x2+ax-y+6)-(2bx2-3x+5y-1) = 2(1-b)x^2 + (a+3)x +...
值与字母x所取的值无关
1-b=0,a+3=0
a=-3,b=1
1/3 a^2 - (2b^2-(1/4 a^2-3b^2))
= 1/3 a^2 - 2b^2 + (1/4 a^2-3b^2)
= 1/3 a^2 - 2b^2 + 1/4 a^2 - 3b^2
= (1/3+1/4)a^2 - 5b^2
= (7/12)*(-3)^2 - 5*1^2
= 21/4 - 5
= 1/4
1年前
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