Solve (2x-1/2)(x-2¼): Find When Function is Positive

Question

Look at the function below:

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

Then determine for which values of x x the following is true:

f(x) > 0

Step-by-Step Solution

To solve this problem, we will examine the intervals defined by the roots of the quadratic function.

Step 1: Find the roots of each factor:
For 2x12=0 2x - \frac{1}{2} = 0 , solve for x x :
2x=12x=14 2x = \frac{1}{2} \quad \Rightarrow \quad x = \frac{1}{4}
For x214=0 x - 2\frac{1}{4} = 0 , solve for x x :
x=214 x = 2\frac{1}{4}

Step 2: Determine the test intervals around these roots, which are x<14 x < \frac{1}{4} , 14<x<214 \frac{1}{4} < x < 2\frac{1}{4} , and x>214 x > 2\frac{1}{4} .

Step 3: Test each interval to determine where the product is positive:

  • For x<14 x < \frac{1}{4} , both factors (2x12) (2x - \frac{1}{2}) and (x214) (x - 2\frac{1}{4}) are negative, so the product is positive.
  • For 14<x<214 \frac{1}{4} < x < 2\frac{1}{4} , one factor is positive (2x12)(2x - \frac{1}{2}) and the other is negative (x214)(x - 2\frac{1}{4}), resulting in a negative product.
  • For x>214 x > 2\frac{1}{4} , both factors (2x12) (2x - \frac{1}{2}) and (x214) (x - 2\frac{1}{4}) are positive, so the product is positive.

Therefore, the solution for f(x)>0 f(x) > 0 is when x>214 x > 2\frac{1}{4} or x<14 x < \frac{1}{4} .

The correct choice that matches this analysis is:
x>214 x > 2\frac{1}{4} or x<14 x < \frac{1}{4} .

Answer

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