推 thdkuo:Q20把他換成指數的方式解 09/24 22:40
→ thdkuo:[√(2x)-√x]/x = [(2x)^(1/2) - x^(1/2)]*x(-1) 09/24 22:42
→ thdkuo:= [2^(1/2)x^(-1/2) - x^(-1/2)] 09/24 22:43
→ thdkuo:= x^(-1/2) * [2^(1/2) - 1] 09/24 22:44
→ thdkuo:= (√2-1)/√x 09/24 22:45
Q20:
If x > 0, then 1/[√(2x)+√x] = ? 答案是D.(√2-1)/√x
我把分子分母同時乘上[√(2x)-√x]變成[√(2x)-√x]/x
可是接下來怎麼約分成答案呢?
Q25:
A photographer will arrange 6 people of 6 different heights for photograph by
placing them in two rows of three so that each person in the first row is
standing in front of someone in the second row. The heights of the people
within each row must increase from left to right, and each person in the
second row must be taller than the person standing in front of him or her.
How many such arrangements of the 6 people are possible?
答案是5種, 可是我怎麼想都只有一組解阿..假設身高由低到高是1-6
row one 123
row two 456
還是我哪裡有盲點 請指教!
Q31:
A positive integer n is said to be “prime-saturated” if the product of all
the different positive prime factors of n is less than the square root of n.
What is the greatest two-digit prime-saturated integer?
答案是96 (請問prime-saturated是什麼?)
此題怎解呢?
麻煩了..tks
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