解:(1)(﹣8a4b5c)÷(4ab5)×(3a3b2), =﹣2a3c×(3a3b2), =﹣6a6b2c; (2)[2(a2x)3﹣9ax5]÷(3ax3), =[2a6x3﹣9ax5]÷(3ax3), =; (3)(3mn+1)(﹣1+3mn)﹣(3mn﹣2)2, =(9m2n2﹣1)﹣(9m2n2﹣12mn+4), =9m2n2﹣1﹣9m2n2+12mn﹣4, =12mn﹣5; (4)1232﹣124×122, =1232﹣(123+1)×(123﹣1), =1232﹣(1232﹣1), =1232﹣1232+1, =1; (5)[(xy+2)(xy﹣2)﹣2x2y2+4]÷(xy), =[x2y2﹣4﹣2x2y2+4]÷(xy), =(﹣x2y2)÷(xy), =﹣xy; 当x=10,y=﹣时,原式=﹣10×(﹣)=. |