Math Problem Statement

Nếu hàm số y = ax^2 + bx + c có a < 0, b < 0 và c > 0 thì đồ thị của nó có dạng?

Solution

This is a question about determining the graph of a quadratic function y=ax2+bx+cy = ax^2 + bx + c based on the given conditions:

  1. a<0a < 0: The coefficient of x2x^2 is negative, so the parabola opens downwards.
  2. b<0b < 0: The coefficient of xx affects the symmetry and position of the vertex, but it doesn't directly determine whether the parabola opens up or down.
  3. c>0c > 0: The constant cc is positive, so the yy-intercept is above the xx-axis.

Based on these conditions:

  • The parabola opens downwards (a<0a < 0).
  • The yy-intercept is above the xx-axis (c>0c > 0).
  • The vertex will likely be in the left half-plane (b<0b < 0).

From the given graphs, the correct choice is D, as it is the only one with a downward-opening parabola with a yy-intercept above the xx-axis.


Let me know if you'd like further explanation! Here are some related questions:

  1. What happens to the graph if a>0a > 0 but c>0c > 0?
  2. How does bb influence the symmetry of the parabola?
  3. Can a quadratic function have more than one yy-intercept? Why or why not?
  4. What is the equation of the axis of symmetry for a quadratic function?
  5. How does the discriminant Δ=b24ac\Delta = b^2 - 4ac affect the shape of the parabola?

Tip: The sign of aa always determines the opening direction of the parabola (upwards if a>0a > 0, downwards if a<0a < 0).

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Math Problem Analysis

Mathematical Concepts

Quadratic Functions
Graph Analysis

Formulas

y = ax^2 + bx + c

Theorems

Direction of Parabola Opening
Vertex Position Based on Coefficients

Suitable Grade Level

Grades 9-12