图 AA, BB, CC, DD, EE 和 FF 展示了六个不同函数的图像。 选择最符合下列特征的图像:

  1. (a)

    yy 与 xx 成反比,

    图像 ...

  2. (b)

    y=xny = x^n,其中 nn 是大于 1 的奇整数,

    图像 ...

  3. (c)

    y=nxy = n^x,其中 nn 是大于 1 的整数。

    图像 ...

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完整解法

6(a)

1. Express the inverse proportion relationship as a linear equation

If yy is inversely proportional to xx, then y=kxy = \frac{k}{x} for some constant k>0k > 0.
This can be rewritten in linear form as y=k(1x)y = k \left(\frac{1}{x}\right).

2. Identify the corresponding graph

Plotting yy against 1x\frac{1}{x} yields a straight line passing through the origin with gradient kk. Diagram A shows a straight line graph of yy against 1x\frac{1}{x} starting from the origin.

答案

A

6(b)

1. Identify the key features of the graph of $y = x^n$ for an odd integer $n > 1$

For y=xny = x^n where nn is an odd integer greater than 1 (e.g., n=3n=3):

  • The graph passes through the origin (0,0)(0,0).
  • It is an odd function, meaning it has rotational symmetry about the origin (it lies in the first and third quadrants).
  • The gradient dydx=nxn−1\frac{dy}{dx} = nx^{n-1} is 00 at x=0x=0, meaning the curve has a horizontal tangent at the origin.
  • As xx increases, the gradient increases, making the curve steeper.

2. Select the matching diagram

Diagram E shows a curve passing through the origin, lying in the first and third quadrants, and flattening out (horizontal tangent) at the origin before becoming steeper. This matches the properties of y=xny = x^n for odd n>1n > 1. (Diagram F has a vertical tangent at the origin, which corresponds to y=x1/ny = x^{1/n}).

答案

E

6(c)

1. Identify the characteristics of the graph of $y = n^x$ for $n > 1$

The function y=nxy = n^x where n>1n > 1 represents exponential growth. The graph must lie entirely above the xx-axis (y>0y > 0), pass through (0,1)(0, 1), and increase rapidly as xx increases.

2. Match the characteristics to the given diagrams

Diagram B shows a curve that is entirely above the xx-axis, has a positive yy-intercept, and increases exponentially from left to right. This matches the properties of y=nxy = n^x.

答案

B

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