Question

若x=30，那么

x

x-3

-

x+6

x2-3x

+

1

x

的值为______．

Answer 1

x

x-3

-

x+6

x2-3x

+

1

x

=

x

x-3

-

x+6

x(x-3)

+

1

x

=

x2

x(x-3)

-

x+6

x(x-3)

+

x-3

x(x-3)

=

x2-x-6+x-3

x(x-3)

=

x2-9

x(x-3)

=

(x+3)(x-3)

x(x-3)

=

x+3

x

，
当x=30时，原式=

30+3

30

=

11

10

．
故答案是：

11

10

．