Math Problem Statement

Bestimmen Sie die Schnittpunkte des Graphen der Funktion f mit den Koordinatenachsen. (Various quadratic equations in German)

Solution

The task requires determining the intersection points of the given functions f(x)f(x) with the coordinate axes, i.e., finding where the functions intersect with the x-axis (roots) and the y-axis (when x=0x = 0).

Let’s go through each function and find these intersections:

  1. Intersection with the y-axis: Set x=0x = 0 to find f(0)f(0).
  2. Intersection with the x-axis: Set f(x)=0f(x) = 0 and solve for xx (this gives the roots).

a) f(x)=1.5x26f(x) = -1.5x^2 - 6

  • Y-axis: f(0)=1.5(0)26=6f(0) = -1.5(0)^2 - 6 = -6 → Intersection at (0,6)(0, -6).
  • X-axis: Solve 1.5x26=0-1.5x^2 - 6 = 0, 1.5x2=6-1.5x^2 = 6, x2=4x^2 = -4 → No real roots (no intersection with x-axis).

b) f(x)=x2+5xf(x) = x^2 + 5x

  • Y-axis: f(0)=(0)2+5(0)=0f(0) = (0)^2 + 5(0) = 0 → Intersection at (0,0)(0, 0).
  • X-axis: x2+5x=0x^2 + 5x = 0, x(x+5)=0x(x + 5) = 0 → Roots x=0x = 0 and x=5x = -5 → Intersections at (0,0)(0, 0) and (5,0)(-5, 0).

c) f(x)=x24x45f(x) = x^2 - 4x - 45

  • Y-axis: f(0)=(0)24(0)45=45f(0) = (0)^2 - 4(0) - 45 = -45 → Intersection at (0,45)(0, -45).
  • X-axis: Solve x24x45=0x^2 - 4x - 45 = 0, factor as (x9)(x+5)=0(x - 9)(x + 5) = 0, roots x=9x = 9 and x=5x = -5 → Intersections at (9,0)(9, 0) and (5,0)(-5, 0).

d) f(x)=(x+1.5)(x+3.5)f(x) = (x + 1.5)(x + 3.5)

  • Y-axis: f(0)=(0+1.5)(0+3.5)=1.5×3.5=5.25f(0) = (0 + 1.5)(0 + 3.5) = 1.5 \times 3.5 = 5.25 → Intersection at (0,5.25)(0, 5.25).
  • X-axis: Solve (x+1.5)(x+3.5)=0(x + 1.5)(x + 3.5) = 0, roots x=1.5x = -1.5 and x=3.5x = -3.5 → Intersections at (1.5,0)(-1.5, 0) and (3.5,0)(-3.5, 0).

e) f(x)=x23x+2f(x) = x^2 - 3x + 2

  • Y-axis: f(0)=(0)23(0)+2=2f(0) = (0)^2 - 3(0) + 2 = 2 → Intersection at (0,2)(0, 2).
  • X-axis: Solve x23x+2=0x^2 - 3x + 2 = 0, factor as (x1)(x2)=0(x - 1)(x - 2) = 0, roots x=1x = 1 and x=2x = 2 → Intersections at (1,0)(1, 0) and (2,0)(2, 0).

f) f(x)=12x2+4x10f(x) = \frac{1}{2}x^2 + 4x - 10

  • Y-axis: f(0)=12(0)2+4(0)10=10f(0) = \frac{1}{2}(0)^2 + 4(0) - 10 = -10 → Intersection at (0,10)(0, -10).
  • X-axis: Solve 12x2+4x10=0\frac{1}{2}x^2 + 4x - 10 = 0, multiply through by 2: x2+8x20=0x^2 + 8x - 20 = 0. Use the quadratic formula: x=8±824(1)(20)2(1)=8±64+802=8±1442=8±122x = \frac{-8 \pm \sqrt{8^2 - 4(1)(-20)}}{2(1)} = \frac{-8 \pm \sqrt{64 + 80}}{2} = \frac{-8 \pm \sqrt{144}}{2} = \frac{-8 \pm 12}{2} Roots: x=2x = 2 and x=10x = -10 → Intersections at (2,0)(2, 0) and (10,0)(-10, 0).

g) f(x)=(x2)21f(x) = (x - 2)^2 - 1

  • Y-axis: f(0)=(02)21=41=3f(0) = (0 - 2)^2 - 1 = 4 - 1 = 3 → Intersection at (0,3)(0, 3).
  • X-axis: Solve (x2)21=0(x - 2)^2 - 1 = 0, (x2)2=1(x - 2)^2 = 1, x2=±1x - 2 = \pm 1, so x=3x = 3 and x=1x = 1 → Intersections at (3,0)(3, 0) and (1,0)(1, 0).

Let me know if you want further clarifications or have any specific questions.

Here are 5 relative questions to expand your understanding:

  1. How can we determine the number of intersections a quadratic function has with the x-axis?
  2. What is the significance of the discriminant in finding the roots of quadratic equations?
  3. How does factoring help in finding the roots of polynomial functions?
  4. How do transformations of basic quadratic functions affect their intersections with the axes?
  5. Can a quadratic function have no real intersections with the x-axis? Why?

Tip: For quadratic equations, always check if factoring is possible before using the quadratic formula—it often simplifies the solution!

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Graphical Analysis

Formulas

Quadratic equation: ax^2 + bx + c = 0
Factorization of quadratic functions
Quadratic formula: x = (-b ± √(b² - 4ac)) / 2a

Theorems

Fundamental Theorem of Algebra
Quadratic Formula

Suitable Grade Level

Grades 8-10