Solve y=2x²+16: Finding Values Where Function is Negative

Question

Given the function:

y=2x2+16 y=2x^2+16

Determine for which values of x the following holds: f(x) < 0

Step-by-Step Solution

To solve this problem, consider the function y=2x2+16 y = 2x^2 + 16 . Our objective is to find values of x x for which y<0 y < 0 .

The function, y=2x2+16 y = 2x^2 + 16 , is a quadratic function in standard form. Here, a=2 a = 2 , b=0 b = 0 , and c=16 c = 16 .

  • Step 1: Determine the Vertex
    Since the quadratic is in the form y=ax2+bx+c y = ax^2 + bx + c , with a>0 a > 0 , it opens upwards. Therefore, its vertex represents the minimum point. The x-coordinate of the vertex is given by x=b2a=04=0 x = \frac{-b}{2a} = \frac{0}{4} = 0 . Substituting x=0 x = 0 into the function provides y=2(0)2+16=16 y = 2(0)^2 + 16 = 16 .
  • Step 2: Analyze the Discriminant
    The discriminant D=b24ac=024×2×16=128 D = b^2 - 4ac = 0^2 - 4 \times 2 \times 16 = -128 . Since D<0 D < 0 , the quadratic has no real roots, meaning it does not cross the x-axis. Instead, it remains entirely above the x-axis.

Since the discriminant is negative, the function has no real roots, confirming that the quadratic function never takes a value below zero. The vertex is at y=16 y = 16 , which is above zero, indicating all function values are positive.

Therefore, the function y=2x2+16 y = 2x^2 + 16 is never less than zero, implying that there are no values of x x for which y<0 y < 0 .

Hence, the solution is No x.

Answer

No x