Solve (x-4.4)(x-2.3) < 0: Finding Negative Function Values

Quadratic Inequalities with Sign Analysis

Look at the function below:

y=(x4.4)(x2.3) y=\left(x-4.4\right)\left(x-2.3\right)

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

f(x)<0 f(x) < 0

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Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Look at the function below:

y=(x4.4)(x2.3) y=\left(x-4.4\right)\left(x-2.3\right)

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

f(x)<0 f(x) < 0

2

Step-by-step solution

To determine when the quadratic function y=(x4.4)(x2.3) y = (x - 4.4)(x - 2.3) is negative, we need to analyze the sign of the product across the different intervals defined by its roots.

  • Step 1: Identify the roots of the function. The roots occur when each factor equals zero, which are x=2.3 x = 2.3 and x=4.4 x = 4.4 .
  • Step 2: Divide the x-axis into intervals based on these roots: x<2.3 x < 2.3 , 2.3<x<4.4 2.3 < x < 4.4 , and x>4.4 x > 4.4 .
  • Step 3: Test a value from each interval:
    • For x<2.3 x < 2.3 , try x=2 x = 2 : y=(24.4)(22.3)=(2.4)(0.3)=0.72 y = (2 - 4.4)(2 - 2.3) = (-2.4)(-0.3) = 0.72 , so the product is positive.
    • For 2.3<x<4.4 2.3 < x < 4.4 , try x=3 x = 3 : y=(34.4)(32.3)=(1.4)(0.7)=0.98 y = (3 - 4.4)(3 - 2.3) = (-1.4)(0.7) = -0.98 , so the product is negative.
    • For x>4.4 x > 4.4 , try x=5 x = 5 : y=(54.4)(52.3)=(0.6)(2.7)=1.62 y = (5 - 4.4)(5 - 2.3) = (0.6)(2.7) = 1.62 , so the product is positive.

From this analysis, we see that the quadratic function is negative for values of x x in the interval 2.3<x<4.4 2.3 < x < 4.4 . This is the range where the function changes sign from positive to negative back to positive.

Therefore, the correct answer is 2.3<x<4.4 2.3 < x < 4.4 .

3

Final Answer

2.3<x<4.4 2.3 < x < 4.4

Key Points to Remember

Essential concepts to master this topic
  • Roots: Set each factor to zero: x = 2.3 and x = 4.4
  • Test Method: Try x = 3 in middle interval: (-1.4)(0.7) = -0.98
  • Verify: Check intervals: negative only between the two roots ✓

Common Mistakes

Avoid these frequent errors
  • Solving the inequality like an equation
    Don't just solve (x-4.4)(x-2.3) = 0 and stop there = missing the inequality part! This only gives you the roots, not where the function is negative. Always test values in each interval to determine the sign.

Practice Quiz

Test your knowledge with interactive questions

The graph of the function below does not intersect the \( x \)-axis.

The parabola's vertex is marked A.

Find all values of \( x \) where
\( f\left(x\right) > 0 \).

AAAX

FAQ

Everything you need to know about this question

Why do I need to find the roots first?

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The roots are where the function changes sign! They divide the number line into intervals where the function stays either positive or negative throughout each interval.

How do I know which interval to test?

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Pick any number from each interval created by the roots. For example, if roots are 2.3 and 4.4, test x = 0 (left), x = 3 (middle), and x = 5 (right).

What if I get the wrong sign when testing?

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Double-check your arithmetic! Remember: negative × negative = positive and negative × positive = negative. Write out each factor's sign clearly.

Why is the answer between the roots?

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This is a upward-opening parabola (positive leading coefficient). It's negative between its roots and positive outside them - like a smile shape!

What does the < symbol mean for the final answer?

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The < symbol means we want where the function is strictly negative (below the x-axis). We don't include the roots themselves since f(2.3)=f(4.4)=0 f(2.3) = f(4.4) = 0 , not negative.

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