Parabola Property Analysis: Vertex Position and Positive Values

Question

If the parabola is bending upwards and its vertex is above the x-axis, then it is always positive.

Step-by-Step Solution

To solve this problem, let's analyze the situation:

  • Given a quadratic function y=ax2+bx+cy = ax^2 + bx + c, if it opens upwards, a > 0.

  • The vertex form of the parabola is y=a(xh)2+ky = a(x-h)^2 + k, where (h,k)(h, k) is the vertex.

  • If the vertex (h,k)(h, k) is above the x-axis, then k > 0.

First, let's restate what it means for a quadratic to be always positive:
This means the function y=ax2+bx+cy = ax^2 + bx + c has no real roots and y > 0 for all xx.

To ensure this, consider:

  • The discriminant Δ=b24ac\Delta = b^2 - 4ac helps determine if the parabola intersects the x-axis.

  • If \Delta < 0, there are no real roots, meaning the parabola doesn't cross the x-axis and stays entirely above it for all xx.

  • Given a > 0 and the vertex is above the x-axis (k > 0), it ensures the function y=a(xh)2+ky = a(x-h)^2 + k stays y > 0.

Therefore, with k > 0 and a > 0, Δ \Delta implies no x-intercepts, confirming the parabola is always positive.

The correct answer is: Correct

Answer

Correct