Solve y=-(4x+32)²: Finding Values Where Function is Positive

Quadratic Functions with Negative Leading Coefficient

Look at the function below:

y=(4x+32)2 y=-\left(4x+32\right)^2

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=(4x+32)2 y=-\left(4x+32\right)^2

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 for which values of x x the function y=(4x+32)2 y = -\left(4x + 32\right)^2 is positive, we must analyze the behavior of this function.

The function y=(4x+32)2 y = -\left(4x + 32\right)^2 is a quadratic function with a negative leading coefficient (the negative sign outside the squared term). This indicates that the parabola opens downwards. Let's break down the expression:

  • The expression inside the parentheses is 4x+32 4x + 32 .
  • Squaring any real number (4x+32)2 \left( 4x + 32 \right)^2 always results in a non-negative value (it is zero or positive).
  • Multiplying this non-negative result by 1-1 makes y y non-positive (either zero or negative).

Since the smallest value (4x+32)2 \left( 4x + 32 \right)^2 can be is zero (when x=8 x = -8 ), and all other values will just make it negative when multiplied by 1-1, y y can never be greater than zero for any real number x x .

Thus, there are no values of x x for which f(x)>0 f(x) > 0 . Consequently, the answer is:

True for no values of x x .

3

Final Answer

True for no values of x x

Key Points to Remember

Essential concepts to master this topic
  • Rule: Negative squared expressions can never be positive
  • Technique: When (4x+32)20 (4x + 32)^2 \geq 0 , then (4x+32)20 -(4x + 32)^2 \leq 0
  • Check: Test vertex at x = -8: y = -(0)² = 0, not positive ✓

Common Mistakes

Avoid these frequent errors
  • Thinking the function is positive when the squared term equals zero
    Don't assume y > 0 when (4x + 32)² = 0 because -(0)² = 0, not positive! Zero is neither positive nor negative. Always remember that multiplying any non-negative value by -1 makes it non-positive.

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 can't this function ever be positive?

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The expression (4x+32)2 (4x + 32)^2 is always non-negative (zero or positive). When you multiply by -1, you flip the sign, making it always non-positive (zero or negative). There's no way to get a positive result!

What happens at x = -8?

+

At x = -8, we get 4(8)+32=0 4(-8) + 32 = 0 , so y=(0)2=0 y = -(0)^2 = 0 . This is the maximum value of the function, but zero is still not positive.

How do I know this parabola opens downward?

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The negative sign in front of the squared term tells you! When the coefficient of the squared term is negative, the parabola opens downward, creating a maximum point instead of a minimum.

Could there be any values where f(x) > 0?

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No, never! Since (4x+32)20 (4x + 32)^2 \geq 0 for all real x, multiplying by -1 gives us (4x+32)20 -(4x + 32)^2 \leq 0 . The function can equal zero but never exceed it.

What if I graphed this function?

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You'd see a downward-opening parabola with its vertex at (-8, 0). The entire graph would be on or below the x-axis, never above it where y would be positive.

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