通过将 frac3x−7(x+3)(x−2)−1\\frac{3x - 7}{(x + 3)(x - 2)} - 1 表示为单个简化分数,精确求解不等式 frac3x−7(x+3)(x−2)<1.\\frac{3x - 7}{(x + 3)(x - 2)} < 1. 由此,精确求解不等式 frac3ex−7(ex+3)(ex−2)<1\\frac{3e^x - 7}{(e^x + 3)(e^x - 2)} < 1。

  1. 通过将 frac3x−7(x+3)(x−2)−1\\frac{3x - 7}{(x + 3)(x - 2)} - 1 表示为单个简化分数,精确求解不等式

    frac3x−7(x+3)(x−2)<1.\\frac{3x - 7}{(x + 3)(x - 2)} < 1.

  2. 由此,精确求解不等式 frac3ex−7(ex+3)(ex−2)<1\\frac{3e^x - 7}{(e^x + 3)(e^x - 2)} < 1。

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完整解法

2[0]

1. Express the given expression as a single simplified fraction.

3x−7(x+3)(x−2)−1=3x−7−(x+3)(x−2)(x+3)(x−2)=3x−7−(x2+x−6)(x+3)(x−2)=−x2+2x−1(x+3)(x−2)=−(x−1)2(x+3)(x−2)\begin{aligned} \frac{3x - 7}{(x + 3)(x - 2)} - 1 &= \frac{3x - 7 - (x + 3)(x - 2)}{(x + 3)(x - 2)} \\ &= \frac{3x - 7 - (x^2 + x - 6)}{(x + 3)(x - 2)} \\ &= \frac{-x^2 + 2x - 1}{(x + 3)(x - 2)} \\ &= \frac{-(x - 1)^2}{(x + 3)(x - 2)} \end{aligned}

2. Set up the rational inequality and determine the required sign of the denominator.

We are solving the inequality −(x−1)2(x+3)(x−2)<0\frac{-(x - 1)^2}{(x + 3)(x - 2)} < 0.
Since the square of any real number is non-negative, (x−1)2≥0(x - 1)^2 \ge 0, which means the numerator −(x−1)2≤0-(x - 1)^2 \le 0.
For the entire fraction to be strictly less than 00, the numerator must be non-zero (so x≠1x \neq 1) and the denominator must be strictly positive:
(x+3)(x−2)>0(x + 3)(x - 2) > 0

3. Solve the quadratic inequality for $x$.

The critical values for the denominator are x=−3x = -3 and x=2x = 2.
The parabola y=(x+3)(x−2)y = (x + 3)(x - 2) opens upwards, so it takes positive values outside the roots:
x<−3orx>2x < -3 \quad \text{or} \quad x > 2
Note that x=1x=1 does not fall in this range, so the condition x≠1x \neq 1 is naturally satisfied.

答案

x<−3 or x>2x < -3 \text{ or } x > 2

2[1]

1. Determine the solution to the inequality from the previous part.

From the previous part, the inequality can be rewritten as:
3x−7(x+3)(x−2)−1<0\frac{3x - 7}{(x + 3)(x - 2)} - 1 < 0
−(x−1)2(x+3)(x−2)<0\frac{-(x - 1)^2}{(x + 3)(x - 2)} < 0
Since −(x−1)2≤0-(x - 1)^2 \le 0 for all real xx and equals 00 when x=1x = 1, the numerator is strictly negative for x≠1x \ne 1.
For the entire fraction to be negative, the denominator must be positive:
(x+3)(x−2)>0andx≠1(x + 3)(x - 2) > 0 \quad \text{and} \quad x \ne 1
Solving this gives:
x<−3orx>2x < -3 \quad \text{or} \quad x > 2

2. Substitute $e^x$ into the established solution.

The new inequality is identical in form to the original, with xx replaced by exe^x. Substituting x=exx = e^x into the solution bounds gives:
ex<−3orex>2e^x < -3 \quad \text{or} \quad e^x > 2

3. Solve for $x$, rejecting any invalid cases.

Since ex>0e^x > 0 for all real xx, the inequality ex<−3e^x < -3 has no real solutions.
We are left with:
ex>2e^x > 2
Taking the natural logarithm on both sides yields:
x>ln⁡2x > \ln 2

答案

x>ln⁡2x > \ln 2

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