Solve (2x-1/2)(x-2.25): Finding Negative Domain Regions

Question

Find the positive and negative domains of the following function:

y=(2x12)(x214) y=\left(2x-\frac{1}{2}\right)\left(x-2\frac{1}{4}\right)

Determine for which values of x x the following is true:

f(x) < 0

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Identify the roots of the quadratic function.
  • Step 2: Analyze the intervals between these roots to determine where the function is negative.
  • Step 3: Write the final solution as the interval where f(x)<0 f(x) < 0 .

Now, let's work through each step:
Step 1: Determine the roots by solving each factor for zero:
- 2x12=02x=12x=14 2x - \frac{1}{2} = 0 \Rightarrow 2x = \frac{1}{2} \Rightarrow x = \frac{1}{4} .
- x214=0x=214 x - 2\frac{1}{4} = 0 \Rightarrow x = 2\frac{1}{4} .
Thus, the roots are x=14 x = \frac{1}{4} and x=214 x = 2\frac{1}{4} .

Step 2: Analyze the intervals determined by the roots x=14 x = \frac{1}{4} and x=214 x = 2\frac{1}{4} :

  • Interval 1: x<14 x < \frac{1}{4}
  • Interval 2: 14<x<214 \frac{1}{4} < x < 2\frac{1}{4}
  • Interval 3: x>214 x > 2\frac{1}{4}

Step 3: Test each interval:

  • For interval 1 x<14 x < \frac{1}{4} : Choose x=0 x = 0 . f(0)=(2(0)12)(0214)=(12)(214)=98>0 f(0) = \left(2(0) - \frac{1}{2}\right)(0 - 2\frac{1}{4}) = \left(-\frac{1}{2}\right) \left(-2\frac{1}{4}\right) = \frac{9}{8} > 0 .
  • For interval 2 14<x<214 \frac{1}{4} < x < 2\frac{1}{4} : Choose x=1 x = 1 . f(1)=(2(1)12)(1214)=(32)(54)=158<0 f(1) = \left(2(1) - \frac{1}{2}\right)(1 - 2\frac{1}{4}) = \left(\frac{3}{2}\right)(-\frac{5}{4}) = -\frac{15}{8} < 0 .
  • For interval 3 x>214 x > 2\frac{1}{4} : Choose x=3 x = 3 . f(3)=(2(3)12)(3214)=(112)(34)=338>0 f(3) = \left(2(3) - \frac{1}{2}\right)(3 - 2\frac{1}{4}) = \left(\frac{11}{2}\right)\left(\frac{3}{4}\right) = \frac{33}{8} > 0 .

Therefore, the solution to f(x)<0 f(x) < 0 is found in the interval 14<x<214 \frac{1}{4} < x < 2\frac{1}{4} .

Answer

\frac{1}{4} < x < 2\frac{1}{4}