Solve y = 3/4x²: Finding Positive Value Domains

Quadratic Functions with Positive Value Analysis

Given the function:

y=34x2 y=\frac{3}{4}x^2

Determine for which values of x f(x)>0 f\left(x\right) > 0 holds

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Step-by-step written solution

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1

Understand the problem

Given the function:

y=34x2 y=\frac{3}{4}x^2

Determine for which values of x f(x)>0 f\left(x\right) > 0 holds

2

Step-by-step solution

To determine where the function y=34x2 y = \frac{3}{4}x^2 is positive, observe:

  • **Step 1:** Identify the nature of the expression x2 x^2 .
    • The expression x2 x^2 is always non-negative for any real number x x , meaning x20 x^2 \geq 0 .
  • **Step 2:** Consider when x2 x^2 equals zero.
    • We see that x2=0 x^2 = 0 only when x=0 x = 0 , as any other value will yield a positive x2 x^2 .
  • **Step 3:** Analyze the entire function.
    • The term 34\frac{3}{4} is positive. Hence, 34x2 \frac{3}{4}x^2 becomes positive whenever x2>0 x^2 > 0 , which implies x0 x \ne 0 .
    • Therefore, for all non-zero x x , y=34x2>0 y = \frac{3}{4}x^2 > 0 .

Thus, the function y=34x2 y = \frac{3}{4}x^2 is positive for all x0 x \ne 0 .

Therefore, the correct answer is x0 x \ne 0 .

3

Final Answer

x0 x\ne0

Key Points to Remember

Essential concepts to master this topic
  • Property: A quadratic x2 x^2 is always non-negative for real numbers
  • Analysis: Since 34>0 \frac{3}{4} > 0 and x20 x^2 \geq 0 , product is positive when x2>0 x^2 > 0
  • Verification: Test x=2 x = 2 : 34(4)=3>0 \frac{3}{4}(4) = 3 > 0 and x=0 x = 0 : 34(0)=0 \frac{3}{4}(0) = 0

Common Mistakes

Avoid these frequent errors
  • Thinking the function is positive for all x values
    Don't assume 34x2>0 \frac{3}{4}x^2 > 0 for ALL x = wrong answer 'All x'! When x = 0, the function equals zero, not positive. Always check what happens at x = 0 since x2=0 x^2 = 0 only when x = 0.

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 isn't the answer 'All x' if the coefficient is positive?

+

Even though 34 \frac{3}{4} is positive, we need f(x) > 0, not just ≥ 0. When x=0 x = 0 , we get 34(0)2=0 \frac{3}{4}(0)^2 = 0 , which is not greater than zero!

How do I know when x2 x^2 is positive vs zero?

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x2=0 x^2 = 0 only when x = 0. For any other real number (positive or negative), x2>0 x^2 > 0 . For example: (3)2=9>0 (-3)^2 = 9 > 0 and 52=25>0 5^2 = 25 > 0 .

What's the difference between > 0 and ≥ 0?

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> 0 means 'greater than zero' (positive), while ≥ 0 means 'greater than or equal to zero' (non-negative). Since we want f(x) > 0, we exclude x = 0 where the function equals zero.

Why does the sign of the coefficient matter?

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The coefficient 34 \frac{3}{4} is positive, so it doesn't change the sign of x2 x^2 . If the coefficient were negative, like 34x2 -\frac{3}{4}x^2 , then the function would be negative (except at x = 0).

Can I test specific values to check my answer?

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Absolutely! Try x = 1: 34(1)2=34>0 \frac{3}{4}(1)^2 = \frac{3}{4} > 0 ✓
Try x = -2: 34(2)2=34(4)=3>0 \frac{3}{4}(-2)^2 = \frac{3}{4}(4) = 3 > 0 ✓
Try x = 0: 34(0)2=0 \frac{3}{4}(0)^2 = 0 (not > 0)

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