Math Problem Statement

The function f is defined by f(x) = ax^2 + bx + c, where a, b, and c are integer constants. The graph of y = f(x) in the xy-plane intersects the x-axis at the points (-5, 0) and (2, 0). If a is greater than 2, what is the greatest possible value of the y-intercept of function f?

A. -18 B. -19

Solution

To determine the greatest possible value of the y-intercept of the function f(x)=ax2+bx+cf(x) = ax^2 + bx + c, given that a>2a > 2 and the roots of the function are x=5x = -5 and x=2x = 2, we need to find the values of aa, bb, and cc that satisfy these conditions.

Since the roots of the quadratic function f(x)=0f(x) = 0 are x=5x = -5 and x=2x = 2, we can write f(x)f(x) in its factored form: f(x)=a(x+5)(x2)f(x) = a(x + 5)(x - 2)

Next, expand this expression: f(x)=a(x22x+5x10)f(x) = a(x^2 - 2x + 5x - 10) f(x)=a(x2+3x10)f(x) = a(x^2 + 3x - 10)

Thus, the coefficients are: a=aa = a b=3ab = 3a c=10ac = -10a

The y-intercept of the function f(x)f(x) occurs when x=0x = 0, so: f(0)=c=10af(0) = c = -10a

We need to maximize the y-intercept, which means we need to find the maximum value of 10a-10a given that a>2a > 2.

Since aa must be an integer greater than 2, the smallest integer greater than 2 is 3. To maximize 10a-10a, we choose the smallest possible aa: a=3a = 3

Now, calculate the y-intercept using a=3a = 3: c=10a=10×3=30c = -10a = -10 \times 3 = -30

Therefore, the greatest possible value of the y-intercept is 30-30.

It appears I made an error in calculations. Given a=3a = 3, the correct maximum value should be c=10×3=30c = -10 \times 3 = -30.

Apologies for any confusion, let's verify the available choices. From the options given: A. -18 B. -19

With a>2a > 2 and using the smallest integer a=3a = 3, the correct maximum possible value of the y-intercept cc was incorrectly stated above. Given that a=3a = 3 indeed results in 30-30.

The correct response based on the initial input should ideally be validated from the given values: None of the given choices. The correct maximum possible y-intercept, calculated carefully, results in -30.

Would you like more details or have any questions? Here are 5 questions you might ask next:

  1. How do you determine the vertex form of a quadratic function?
  2. Can you explain the significance of the discriminant in quadratic equations?
  3. What are some real-world applications of quadratic functions?
  4. How can the roots of a quadratic function be found using the quadratic formula?
  5. What is the impact of the coefficient aa on the graph of a quadratic function?

Tip: Always cross-verify the constraints and available options carefully to ensure the chosen result aligns with expectations.

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Math Problem Analysis

Mathematical Concepts

Quadratic Equations
Roots of Polynomials

Formulas

Quadratic function formula: f(x) = ax^2 + bx + c
Factoring quadratic equations

Theorems

Properties of quadratic functions

Suitable Grade Level

Grades 10-12