计算 (1)(−48a6b5c)÷(24ab4)•(−5/6a5b2); (2)(2s-3t+1)(2s+3t-1).

问题描述:

计算
(1)(−48a6b5c)÷(24ab4)•(−

5
6
a5b2);
(2)(2s-3t+1)(2s+3t-1).

(1)原式=-2a5bc•(-

5
6
a5b2
=
5
3
a10b3c;
(2)原式=[2s-(3t-1)][2s+(3t-1)]
=(2s)2-(3t-1)2
=4s2-9t2+6t-1.