(3mn+1)(3mn-1)-(3mn-2)²和(2/5mn³-m²n²+1/6n的4此方)/(2/3n²完整的计算过程!

问题描述:

(3mn+1)(3mn-1)-(3mn-2)²和(2/5mn³-m²n²+1/6n的4此方)/(2/3n²完整的计算过程!

顶楼上!

解 (3mn+1)(3mn-1)-(3mn-2)²=(3mn)²-1²-[(3mn)²-2×3mn×2+2²]=9m²n²-1-(9m²n²-12mn+4)=9m²n²-1-9m²n²+12mn-4=12mn-5(2/5mn³-m²n²...