Determining Negative Regions of the Quadratic: y = -2x² - 8x - 10

Question

Look at the following function:

y=2x28x10 y=-2x^2-8x-10

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

f(x) < 0

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Analyze the quadratic function's graph from given coefficients.
  • Step 2: Calculate discriminant to find root characteristics.
  • Step 3: Discuss the implications on positivity or negativity of f(x) f(x) .

Now, let's work through each step:

Step 1: The quadratic function y=2x28x10 y = -2x^2 - 8x - 10 has a leading coefficient a=2 a = -2 , which is negative. This indicates that the parabola opens downwards, potentially sitting below the x x -axis.

Step 2: Calculate the discriminant Δ=b24ac \Delta = b^2 - 4ac .

Here, b=8 b = -8 , a=2 a = -2 , and c=10 c = -10 . Plug these into the formula:

Δ=(8)24(2)(10)=6480=16 \Delta = (-8)^2 - 4(-2)(-10) = 64 - 80 = -16

Since the discriminant Δ \Delta is negative, there are no real roots. The parabola does not intersect the x x -axis.

Step 3: Discuss implications.

Because the parabola opens downward and has no real roots, it lies entirely below the x x -axis. This means for all real values of x x , f(x)<0 f(x) < 0 .

Therefore, the function y=2x28x10 y = -2x^2 - 8x - 10 is negative for all x x .

The function is negative for all x x .

Answer

The function is negative for all x x .