问题 填空题
已知a=3,b=1,那么2a-5b=______,a2-b3=______,a3-
8
b
=______.
答案

(1)2a-5b,

=2×3-5×1,

=6-5,

=1,

(2)a2-b3,

=32-13

=9-1,

=8,

(3)a3-

8
b

=3×3×3-

8
1

=27-8,

=19,

故答案为:1;8;19.

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