Solve Quadratic Inequality: When is -(2x-2¼)² Greater Than Zero

Quadratic Inequalities with Negative Leading Coefficient

Given the function:

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

Determine for which values of X the following holds:

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

Given the function:

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

Determine for which values of X the following holds:

f(x)>0 f(x) > 0

2

Step-by-step solution

To solve this problem, we begin by analyzing the function y=(2x214)2 y = -\left(2x - 2\frac{1}{4}\right)^2 .

The expression inside the square, 2x214 2x - 2\frac{1}{4} , can take any real value depending on x x . However, when squared (2x214)2 \left(2x - 2\frac{1}{4}\right)^2 , it becomes non-negative for all real x x , meaning it is always greater than or equal to zero.

Since y y is defined as the negative of this square—y=(2x214)2 y = -\left(2x - 2\frac{1}{4}\right)^2 —the function y y is always less than or equal to zero. In other words, y0 y \leq 0 for all real values of x x .

Therefore, there are no values of x x that make f(x)>0 f(x) > 0 , as the function outputs non-positive values exclusively.

Thus, the solution to the problem is No x.

3

Final Answer

No x

Key Points to Remember

Essential concepts to master this topic
  • Sign Rule: Negative times positive squared expression equals negative
  • Technique: Recognize (2x214)20 -(2x-2\frac{1}{4})^2 \leq 0 always holds
  • Check: Test any x value: (2(1)2.25)2=0.56<0 -(2(1)-2.25)^2 = -0.56 < 0

Common Mistakes

Avoid these frequent errors
  • Ignoring the negative sign in front
    Don't think (2x214)2>0 (2x-2\frac{1}{4})^2 > 0 means the whole expression is positive = wrong conclusion! The negative sign makes the entire expression non-positive. Always consider all signs and operations in the correct order.

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 can't this expression ever be positive?

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Because any squared expression is non-negative, and when you put a negative sign in front, it becomes non-positive. So (something)20 -(\text{something})^2 \leq 0 always!

What if I set the expression inside equal to zero?

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Great thinking! When 2x214=0 2x - 2\frac{1}{4} = 0 , we get x=118 x = 1\frac{1}{8} . At this point, the function equals zero, but we need greater than zero.

Could there be a mistake in the problem setup?

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No mistake! This is a valid mathematical scenario. Some inequalities have no solution, just like some equations have no solution. It's an important concept to understand.

How do I know when an inequality has no solution?

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Look for patterns like negative times squared expressions or absolute values less than negative numbers. These create impossible conditions that no real number can satisfy.

What's the difference between 'no solution' and 'all real numbers'?

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'No solution' means no x works for the inequality. 'All real numbers' means every x works. They're opposite situations - be careful not to confuse them!

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