Solve the Quadratic Inequality: When Does y = -4x^2 + 24x Become Positive?

Question

Look at the following function:

y=4x2+24x y=-4x^2+24x

Determine for which values of x x the following is true:

f\left(x\right) > 0

Step-by-Step Solution

To determine the values of x x for which the function y=4x2+24x y = -4x^2 + 24x is greater than zero, we will proceed as follows:

Step 1: Find the roots of the quadratic equation.

We start by solving 4x2+24x=0 -4x^2 + 24x = 0 to find the critical points. This can be factored as:

x(4x+24)=0 x(-4x + 24) = 0

This equation gives us two roots:

  1. x=0 x = 0
  2. 4x+24=0x=6 -4x + 24 = 0 \Rightarrow x = 6

Step 2: Determine intervals for positivity.

The roots divide the number line into three intervals: (,0) (-\infty, 0) , (0,6)(0, 6), and (6,) (6, \infty) .

Since the parabola opens downwards (as indicated by the negative leading coefficient), the function will be positive between the roots:

0<x<6 0 < x < 6

Conclusion: To ensure the function y=4x2+24x y = -4x^2 + 24x is greater than zero, the value of x x must be between 0 and 6.

Therefore, the solution to the problem is 0<x<6 0 < x < 6 .

Answer

0 < x < 6