已知对于 ,有 。
- (a)
写出 的值。
- (b)
求 。
- (c)
说明 是增函数还是减函数。
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完整解法
6(a)
1. Determine the condition for the function to be defined
For to be defined and real, the expression inside the square root in the denominator must be strictly positive.
6(b)
1. Apply the quotient rule to differentiate the function
Let and .
2. Simplify the derivative
Multiply the numerator and the denominator by to eliminate the negative exponent:
6(c)
1. Recall the derivative from part (b) and analyse its sign for the given domain
From part (b), .
For , , so the denominator .
Also, , so the numerator is positive.
2. Conclude whether the function is increasing or decreasing
Since for all , is an increasing function.
Increasing function, since for all .
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