Solve -3x² + 12x > 0: Finding Positive Function Values

Question

Look at the following function:

y=3x2+12x y=-3x^2+12x

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

f(x) > 0

Step-by-Step Solution

To determine where the function f(x)=3x2+12x f(x) = -3x^2 + 12x is greater than zero, we need to find the roots of the equation.

Step 1: Set the function equal to zero to find the zeros or roots:

3x2+12x=0-3x^2 + 12x = 0

Step 2: Factor the equation:

3x(x4)=0-3x(x - 4) = 0

Setting each factor equal to zero gives us the roots:

  • 3x=0x=0-3x = 0 \rightarrow x = 0
  • x4=0x=4x - 4 = 0 \rightarrow x = 4

Step 3: Since the parabola opens downwards (as the coefficient of x2 x^2 is negative), f(x)>0 f(x) > 0 for x x values between the roots. Thus, the function is positive between x=0 x = 0 and x=4 x = 4 .

Therefore, the solution is the interval 0<x<4 0 < x < 4 .

In conclusion, the values of x x for which the function is greater than zero are 0<x<4 0 < x < 4 .

Answer

0 < x < 4