Math Problem Statement

f(x)=-x^2+7x+5 determine the number of x-intercepts of the graph

Solution

To determine the number of xx-intercepts of the function f(x)=x2+7x+5f(x) = -x^2 + 7x + 5, we need to find the points where the graph intersects the xx-axis. These points occur when f(x)=0f(x) = 0, i.e., when:

x2+7x+5=0-x^2 + 7x + 5 = 0

This is a quadratic equation, which we can solve using the discriminant method. For a quadratic equation of the form ax2+bx+c=0ax^2 + bx + c = 0, the discriminant is given by:

Δ=b24ac\Delta = b^2 - 4ac

For the equation x2+7x+5=0-x^2 + 7x + 5 = 0, the coefficients are:

  • a=1a = -1
  • b=7b = 7
  • c=5c = 5

Now, calculate the discriminant:

Δ=(7)24(1)(5)=49+20=69\Delta = (7)^2 - 4(-1)(5) = 49 + 20 = 69

Interpretation of the discriminant:

  • If Δ>0\Delta > 0, there are two distinct real roots, meaning the graph intersects the xx-axis at two points.
  • If Δ=0\Delta = 0, there is one real root (the vertex touches the xx-axis).
  • If Δ<0\Delta < 0, there are no real roots, meaning the graph does not intersect the xx-axis.

Since Δ=69>0\Delta = 69 > 0, there are two distinct real roots, which means the graph has two x-intercepts.


Would you like to see the exact points of intersection? Or would you like to explore other aspects of the quadratic function?

Here are some related questions:

  1. How do you find the exact x-intercepts of a quadratic function?
  2. What does the discriminant tell you about the shape of a quadratic graph?
  3. How do you determine whether a quadratic function opens upwards or downwards?
  4. What is the vertex of the quadratic function f(x)=x2+7x+5f(x) = -x^2 + 7x + 5?
  5. How can you find the axis of symmetry for a quadratic function?

Tip: The discriminant is very useful for quickly determining the number of real roots of a quadratic equation without having to fully solve it.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Discriminant
X-Intercepts

Formulas

Quadratic equation formula ax^2 + bx + c = 0
Discriminant formula Δ = b^2 - 4ac

Theorems

Discriminant theorem

Suitable Grade Level

Grades 9-11