Solve the Inequality: Finding Where f(x) > 0 on the Graph

Quadratic Inequalities with Graphical Analysis

Find all values of x x

where f(x)>0 f\left(x\right) > 0 .

XXXYYY555

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1

Understand the problem

Find all values of x x

where f(x)>0 f\left(x\right) > 0 .

XXXYYY555

2

Step-by-step solution

The problem requires us to determine where the function f(x) f(x) , depicted in the graph, is greater than 0. This interval will be where the graph lies above the x-axis. From the visual representation, the parabola intersects the x-axis at x=5 x = 5 .

Given it is a standard parabola opening upwards or downwards, we need to determine the regions of positivity based on its graph above the x-axis. Usually, a quadratic function, if it opens upwards, has negative values between its roots, provided there's a minimum point. If it opens downwards, the opposite is true.

From the graph, observe that the parabola is indeed below the x-axis at point x=5 x = 5 . The function is positive on both sides away from the point where it intersects (the ends of the parabola ascend back above the x-axis).

To find the solution, notice:

  • At x=5 x = 5 , the function equals zero at this point.
  • The function is positive on the intervals x<5 x < 5 and x>5 x > 5 .

Thus, the values of x x for which f(x)>0 f(x) > 0 are on the intervals (,5)(-\infty, 5) and (5,)(5, \infty).

The function f(x) f(x) is positive for x<5 x < 5 or x>5 x > 5 . Therefore, the correct answer is: x<5 x < 5 or x>5 x > 5 .

3

Final Answer

x<5 x < 5 or x>5 x > 5

Key Points to Remember

Essential concepts to master this topic
  • Reading Graphs: Function is positive when curve lies above x-axis
  • Technique: At x=5 x = 5 , function equals zero; positive everywhere else
  • Check: Test points like x=0 x = 0 and x=10 x = 10 to confirm both are positive ✓

Common Mistakes

Avoid these frequent errors
  • Including the zero point in the solution
    Don't write x5 x \leq 5 or x5 x \geq 5 when solving f(x)>0 f(x) > 0 = includes where function equals zero! The inequality asks for strictly greater than zero, not greater than or equal to. Always use strict inequality symbols when the question asks for f(x)>0 f(x) > 0 .

Practice Quiz

Test your knowledge with interactive questions

The graph of the function below intersects the X-axis at points A and B.

The vertex of the parabola is marked at point C.

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

AAABBBCCCX

FAQ

Everything you need to know about this question

Why isn't x = 5 included in the answer?

+

Because at x=5 x = 5 , the function equals zero, not a positive value. The question asks for f(x)>0 f(x) > 0 , which means strictly greater than zero.

How do I know the function is positive on both sides of x = 5?

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Look at the graph! The parabola dips down to touch the x-axis at x=5 x = 5 , but rises above the x-axis on both sides. This means it's positive for x<5 x < 5 and x>5 x > 5 .

What's the difference between > and ≥ in inequalities?

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> means "greater than" (doesn't include the boundary point)
means "greater than or equal to" (includes the boundary point)
Since f(5)=0 f(5) = 0 , we use > because 0 is not greater than 0!

Can I write the answer as one interval instead of two?

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No! The solution x<5 x < 5 or x>5 x > 5 represents two separate intervals: (,5)(5,) (-\infty, 5) \cup (5, \infty) . There's a "gap" at x=5 x = 5 where the function is not positive.

What if the parabola opened downward instead?

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If the parabola opened downward and touched the x-axis at x=5 x = 5 , then f(x)>0 f(x) > 0 would have no solution because the function would be negative everywhere except at the single point where it equals zero.

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