计算：[9a^2-3)^2-3(a^2+3)]除以3a^2
4个回答
1、[9a^2-3)^2-3(a^2+3)]除以3a^2
=[81a^4 +9-54a^2 -3a^2-9]/(3a^2)
=[81a^4 -57a^2]/(3a^2)
=27a^2 -19
2、原式=[(a^2+1)/(a^2-1)]+[1/(a-1)]-[1/(a+1)]
=[(a^2+1)/(a^2-1)]+[(a+1)/(a^2 -1)]-[(a-1)/(a^2-1)]
=[(a^2 +1)+(a+1)-(a-1)]/(a^2-1)
=(a^2 +3)/(a^2-1)
3、原式=x^2 (x+3)-9(x+3)
=(x-3)(x+3)^2
4、原式=9a^2 -12ab+9b^2
5、原式=[y/(y^2-x^2)]-[(y-x)/(y^2-x^2)]
=x/(y^2-x^2)
6、原式=a^(m+2n)
=(a^m) *[(a^n)^2]
=2*3^2
=18
7、(x^2-y^2)/(x+y)=x-y
(2x-2y)/(x-y)=2
即 扩大2倍
答案选B
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