Given the function:
y=2x2+16
Determine for which values of x the following holds: f(x) < 0
To solve this problem, consider the function y=2x2+16. Our objective is to find values of x for which y<0.
The function, y=2x2+16, is a quadratic function in standard form. Here, a=2, b=0, and c=16.
- Step 1: Determine the Vertex
Since the quadratic is in the form y=ax2+bx+c, with a>0, it opens upwards. Therefore, its vertex represents the minimum point. The x-coordinate of the vertex is given by x=2a−b=40=0. Substituting x=0 into the function provides y=2(0)2+16=16.
- Step 2: Analyze the Discriminant
The discriminant D=b2−4ac=02−4×2×16=−128. Since 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, which is above zero, indicating all function values are positive.
Therefore, the function y=2x2+16 is never less than zero, implying that there are no values of x for which y<0.
Hence, the solution is No x.