- (i)
画出方程为 的曲线 的草图,写出其与坐标轴的交点的精确坐标以及所有渐近线的方程。
- (ii)
通过在草图中添加一条直线,解不等式 。
- (iii)
由此,解不等式 。
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完整解法
2(i)
1. Find the equations of the vertical and horizontal asymptotes.
The vertical asymptote occurs where the denominator is zero:
The horizontal asymptote is found by examining the behaviour as , or by polynomial division:
As , , so the horizontal asymptote is:
2. Determine the exact coordinates of the intersections with the axes.
For the -axis intersection, substitute :
Coordinates are .
For the -axis intersection, substitute :
Coordinates are .
3. Sketch the curve, clearly labelling the asymptotes and intercepts.
[Sketch of a hyperbola with dashed lines for asymptotes and .
The top-left branch passes through the -intercept and approaches both asymptotes.
The bottom-right branch passes through the -intercept and approaches both asymptotes.]
Asymptotes:
Intercepts:
[A smooth hyperbolic curve with branches in the top-left and bottom-right relative to the asymptotes' intersection at ]
2(ii)
1. Identify the equation of the line to be drawn.
To solve graphically, we use the sketched curve with equation .
We must draw the additional line on the same axes.
2. Determine the points of intersection between the curve and the line.
The line has an -intercept at and a -intercept at .
These coordinates exactly match the axes intercepts of the curve found in part (i), meaning the line intersects the curve exactly at the points and .
3. Use the graph to deduce the solution to the inequality.
The inequality is satisfied where the curve lies below or on the line .
Observing the relative positions of the graphs and noting the vertical asymptote at :
- For , the curve is below or on the line.
- For , the curve is above the line.
- For , the curve is below or on the line (excluding the asymptote ).
- For , the curve is above the line.
Thus, the required range of values is .
2(iii)
1. Concisely find the solution to the inequality from part (ii).
From part (ii), we solve :
The critical values are , (asymptote), and . Evaluating the signs in the intervals between these values yields the solution for part (ii):
2. Apply the substitution $x \to |x|$ into the solution from part (ii).
The inequality in (iii) is identical to (ii) except is replaced by . Thus, we substitute into our solution:
3. Solve the resulting modulus inequalities.
For the first condition, since for all real :
For the second condition, solving the compound modulus inequality yields:
Combining these conditions gives the final solution set:
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