Math Problem Statement

Here is a sketch of a curve. The equation of the curve is y = x^2 + ax + b, where a and b are integers. The points (0, -5) and (5, 0) lie on the curve. Find the coordinates of the turning point of the curve.

Solution

The problem asks to find the coordinates of the turning point of the curve given by the quadratic equation y=x2+ax+by = x^2 + ax + b. We know that:

  • The points (0,5)(0, -5) and (5,0)(5, 0) lie on the curve.
  • aa and bb are integers.

Step 1: Substituting the points into the equation

Using the point (0,5)(0, -5):

y=x2+ax+bat(0,5):y = x^2 + ax + b \quad \text{at} \, (0, -5): 5=02+a(0)+b    b=5-5 = 0^2 + a(0) + b \implies b = -5

Using the point (5,0)(5, 0):

y=x2+ax+bat(5,0):y = x^2 + ax + b \quad \text{at} \, (5, 0): 0=52+a(5)5    0=25+5a5    5a=20    a=40 = 5^2 + a(5) - 5 \implies 0 = 25 + 5a - 5 \implies 5a = -20 \implies a = -4

Thus, the equation of the curve becomes:

y=x24x5y = x^2 - 4x - 5

Step 2: Finding the turning point

The turning point (vertex) of a parabola y=x2+ax+by = x^2 + ax + b occurs at x=a2x = -\frac{a}{2}. In this case:

x=42=2x = -\frac{-4}{2} = 2

To find the corresponding yy-coordinate, substitute x=2x = 2 into the equation:

y=224(2)5=485=9y = 2^2 - 4(2) - 5 = 4 - 8 - 5 = -9

Final Answer:

The turning point of the curve is (2,9)(2, -9).

Would you like more details on any step or have any further questions?

Here are 5 follow-up questions to extend your understanding:

  1. How can you verify the turning point of a quadratic equation using calculus?
  2. What is the general form of the equation for the vertex of any parabola y=ax2+bx+cy = ax^2 + bx + c?
  3. How does the value of aa in the equation affect the shape and direction of the parabola?
  4. How do you determine whether the turning point is a maximum or minimum for a quadratic function?
  5. What role does the discriminant play in determining the number of real roots of a quadratic equation?

Tip: The turning point of a quadratic function can be easily found using the formula x=b2ax = -\frac{b}{2a} for the vertex, where bb and aa are coefficients from the general form ax2+bx+cax^2 + bx + c.

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Math Problem Analysis

Mathematical Concepts

Quadratic Equations
Parabolas
Coordinate Geometry

Formulas

y = ax^2 + bx + c
Turning point formula: x = -b/2a

Theorems

Properties of Quadratic Functions
Vertex form of a parabola

Suitable Grade Level

Grades 9-11