搜搜考试网问几道数学题,英语好的进!
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问几道数学题,英语好的进!
1.An integer is chosen at random from 1000 to 9999.Find the probability of choosing an integer having 4 different digits such that the difference between the first and last digits is 2.
2.A={(x,y):3x-y=29} and B={(x,y):2y+5x=52}.Find A∩B
3.It is known that n(A) =10,n(B) =4 and n(∑) =11.Calculate the maximum and minimum values of the following:n(A∪B),n(A∩B),n(A∪B′),
我要的是working and answer，题目看的懂的说。
1.An integer is chosen at random from 1000 to 9999.Find the probability of choosing an integer having 4 different digits such that the difference between the first and last digits is 2.
2.A={(x,y):3x-y=29} and B={(x,y):2y+5x=52}.Find A∩B
3.It is known that n(A) =10,n(B) =4 and n(∑) =11.Calculate the maximum and minimum values of the following:n(A∪B),n(A∩B),n(A∪B′),
我要的是working and answer，题目看的懂的说。
1.1000-9999 选出四个数位都不相同且千位,个位相差2的概率
千位各位相差2 只有97,86,75,64,53,42,31,20,13,24,35,46,57,68,79十五种可能 任一组合 十位,百位均有8*7=56种 则共计56*15=840种,概率为840/9000=7/75
2.已知A={(x,y):3x-y=29} and B={(x,y):2y+5x=52}.求 A∩B
A={(x,y):3x-y=29}表示 直线3x-y=29上的点集 ,B={(x,y):2y+5x=52}表示直线2y+5x=52上的点集,A∩B是两直线交点的点集.联立3x-y=29,2y+5x=52即可,得x=10,y=1则A∩B=｛（10,1）｝
3.已知 n(A) =10,n(B) =4 and n(∑) =11,求 n(A∪B),n(A∩B),n(A∪B′)的最大值和最小值
先最大值：maximum values of n(A∪B)=11,maximum values of n(A∩B)=4,maximum values of n(A∪B′)=11
再最小值：minimum values of n(A∪B)=10,minimum values of n(A∩B)=3,minimum values of n(A∪B′)=10
千位各位相差2 只有97,86,75,64,53,42,31,20,13,24,35,46,57,68,79十五种可能 任一组合 十位,百位均有8*7=56种 则共计56*15=840种,概率为840/9000=7/75
2.已知A={(x,y):3x-y=29} and B={(x,y):2y+5x=52}.求 A∩B
A={(x,y):3x-y=29}表示 直线3x-y=29上的点集 ,B={(x,y):2y+5x=52}表示直线2y+5x=52上的点集,A∩B是两直线交点的点集.联立3x-y=29,2y+5x=52即可,得x=10,y=1则A∩B=｛（10,1）｝
3.已知 n(A) =10,n(B) =4 and n(∑) =11,求 n(A∪B),n(A∩B),n(A∪B′)的最大值和最小值
先最大值：maximum values of n(A∪B)=11,maximum values of n(A∩B)=4,maximum values of n(A∪B′)=11
再最小值：minimum values of n(A∪B)=10,minimum values of n(A∩B)=3,minimum values of n(A∪B′)=10