4114??22???1?1?302?1??8．求A??121113?的秩.

??312?2?1?1???42?2?60?8???

?2x1?x2?x3?1?9.解线性方程组 ?4x1?2x2?5x3?4.

?2x?x?2x?523?1

?2x1?x2?3x3?1?10.解线性方程组 ?4x1?2x2?5x3?4.

?2x?2x3?6?1

11．甲、乙二人依次从装有7个白球，3个红球的袋中随机地摸1个球，求甲、乙摸到不同颜色球的概率.