The problem is to solve the inequality $\frac{x^2 - 3x + 1}{x-3} > 0$.

AlgebraInequalitiesQuadratic EquationsRational ExpressionsInterval Notation
2025/5/25

1. Problem Description

The problem is to solve the inequality x23x+1x3>0\frac{x^2 - 3x + 1}{x-3} > 0.

2. Solution Steps

First, we need to find the zeros of the numerator, x23x+1=0x^2 - 3x + 1 = 0. We can use the quadratic formula to find the roots:
x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}
In our case, a=1a = 1, b=3b = -3, and c=1c = 1. Thus,
x=3±(3)24(1)(1)2(1)x = \frac{3 \pm \sqrt{(-3)^2 - 4(1)(1)}}{2(1)}
x=3±942x = \frac{3 \pm \sqrt{9 - 4}}{2}
x=3±52x = \frac{3 \pm \sqrt{5}}{2}
So, the roots of the numerator are x1=3520.38x_1 = \frac{3 - \sqrt{5}}{2} \approx 0.38 and x2=3+522.62x_2 = \frac{3 + \sqrt{5}}{2} \approx 2.62.
The denominator is x3x-3. The value that makes the denominator zero is x=3x = 3.
Now, we consider the intervals defined by these critical points: (,352)(-\infty, \frac{3 - \sqrt{5}}{2}), (352,3+52)(\frac{3 - \sqrt{5}}{2}, \frac{3 + \sqrt{5}}{2}), (3+52,3)(\frac{3 + \sqrt{5}}{2}, 3), and (3,)(3, \infty). We will test a point in each interval to determine the sign of the expression x23x+1x3\frac{x^2 - 3x + 1}{x-3}.

1. Interval $(-\infty, \frac{3 - \sqrt{5}}{2})$: Let $x = 0$.

023(0)+103=13=13<0\frac{0^2 - 3(0) + 1}{0 - 3} = \frac{1}{-3} = -\frac{1}{3} < 0

2. Interval $(\frac{3 - \sqrt{5}}{2}, \frac{3 + \sqrt{5}}{2})$: Let $x = 1$.

123(1)+113=13+12=12=12>0\frac{1^2 - 3(1) + 1}{1 - 3} = \frac{1 - 3 + 1}{-2} = \frac{-1}{-2} = \frac{1}{2} > 0

3. Interval $(\frac{3 + \sqrt{5}}{2}, 3)$: Let $x = 2.7$.

(2.7)23(2.7)+12.73=7.298.1+10.3=0.190.3<0\frac{(2.7)^2 - 3(2.7) + 1}{2.7 - 3} = \frac{7.29 - 8.1 + 1}{-0.3} = \frac{0.19}{-0.3} < 0

4. Interval $(3, \infty)$: Let $x = 4$.

423(4)+143=1612+11=51=5>0\frac{4^2 - 3(4) + 1}{4 - 3} = \frac{16 - 12 + 1}{1} = \frac{5}{1} = 5 > 0
The inequality x23x+1x3>0\frac{x^2 - 3x + 1}{x-3} > 0 is satisfied in the intervals (352,3+52)(\frac{3 - \sqrt{5}}{2}, \frac{3 + \sqrt{5}}{2}) and (3,)(3, \infty).

3. Final Answer

The solution to the inequality is (352,3+52)(3,)(\frac{3 - \sqrt{5}}{2}, \frac{3 + \sqrt{5}}{2}) \cup (3, \infty).

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