[計量] 好幾題數學問題
麻煩好心的版友可以告訴我解法嗎?
謝謝
因為目前手邊沒有書可以查 ˊˋ
發現很多都忘光了,也不知道要怎麼算
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1.For all real numbers,xy+x=5 and y^2+2y=19
A: x / y+1 B: 1/4
2. How many ways can 2 identical red chairs and 4 identical blue chairs be
arranged in a row?
ANS: 15
3.(n+2)!-(n+1)!/n!= 有人可以告訴我算法嗎??或是有什麼訣竅 謝謝
ANS: (n+1)^2
4. In the xy-coordinate plane, the vertices of the traingle ABC are
A(15,1) B(9,3) C(4,5). What is the slope of the altitude to side AB?
ANS: 3 但是我算的是-1/3,覺得好奇怪@@
5. If the perpendicular bisector of the segment with endpoints A(1,2)and
B(2,4) contains the point (4,C), then the value of C is?
ANS:7/4 完全不知道怎麼算 ˊˋ
6. If a cube has an edge of length 10, then the length of the segment
connecting the center of a face of the cube to any vertex not contained
in the place of the face is?
ANS:5√6
7. If a bowl cintains seven marbles, three red and four green, four marbles
are drawn from the bowl at random without replacement. What is the
probability that contains two red marbles and two green ones?
ANS:18/35 但是我算出來是3/35 請問要怎麼算呢? 謝謝 ^^"
8. After the first term, each term in a sequence is 3 greater than 1/3 of the
preceding term. If t is the first term of the sequence and t =/ 0, what is
the ratio of the second term to the first term??
ANS: t+9/3t
真的很不好意思我問好多題,再次感謝各位板友
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