不使用计算器,求解
- (i)
求解
。
- (ii)
求解
。
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完整解法
6(i)
1. Rearrange the inequality to form a single rational expression compared to zero.
2. Factorise the numerator to identify all critical values.
The critical values are , , and .
3. Use a sign test to determine the intervals that satisfy the inequality, ensuring the denominator is not zero.
Testing the intervals separated by the critical values , , and for the sign of :
- For :
- For :
- For :
- For :
Including the boundaries where the expression equals zero (but excluding where it is undefined), we get:
6(ii)
1. Solve the rational inequality from part (i) to establish the base solution.
To solve part (ii) using the intended sequence, we first explicitly state the solution to part (i):
Using a sign diagram for the critical values , , and , the solution to (i) is:
2. Substitute $x$ with $|x|$ using the relationship between the two inequalities and reject the invalid case.
The inequality in (ii) is identical to (i) but with replaced by . We substitute into the solution from (i):
Since the absolute value of a real number is always non-negative (), the first inequality yields no real solutions.
3. Solve the valid modulus inequality to find the final range of values for $x$.
We solve the remaining inequality :
The condition means .
The condition gives .
Combining these results, the final solution is:
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