在不使用计算器的情况下,解不等式 由此解不等式
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完整解法
3(i)
1. Show that the quadratic factor in the numerator is always positive.
By completing the square for :
Since for all real , it follows that .
Thus, is always strictly positive.
2. Simplify the inequality by removing the positive factor.
Since for all real , dividing both sides of the inequality by this expression will not change the inequality sign.
3. Convert the rational inequality to a polynomial inequality.
Multiply both sides by . Since for , the inequality sign remains unchanged:
Note that to avoid a zero denominator in the original rational expression.
4. Solve the resulting quadratic inequality and deduce the final range.
The critical values for are and .
Because it is a '' inequality with a positive coefficient, the solution lies outside the roots:
However, because (undefined denominator), we reject .
Therefore, the solution is:
3(ii)
1. Concisely solve the inequality from part (i) to find the base solution range.
For the quadratic factor, for all real .
Dividing both sides by this strictly positive factor, the inequality in (i) simplifies to:
By testing intervals around the critical values (where the expression is undefined) and (where it is zero), the solution to (i) is:
2. Substitute $|x|$ for $x$ in the base solution, recognising that $x^2 = |x|^2$.
The inequality in (ii) can be rewritten as:
This is the exact same inequality as in (i), but with replaced by . Using the result from (i), we substitute with to get:
3. Solve the resulting modulus inequalities for $x$.
Since the absolute value of any real number is non-negative (), the inequality has no real solution.
For the remaining inequality:
This gives the solution:
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