Question

计算：[9a^2-3)^2-3(a^2+3)]除以3a^2

Answer 1

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