Math Problem Statement

Pangsa pasar sebuah produk mengalami kenaikan sedangkan barang tersebut mengalami kelangkaan. Sehingga fungsi penawaran barang tersebut menjadi y = 3x^2 + 5x + 1. Jika digambar grafiknya, maka manakah pernyataan berikut ini yang merupakan ciri-ciri grafik fungsi kuadrat tersebut?

Solution

The given function is y=3x2+5x+1y = 3x^2 + 5x + 1, which is a quadratic function of the form y=ax2+bx+cy = ax^2 + bx + c, where a=3a = 3, b=5b = 5, and c=1c = 1. Let’s analyze its characteristics:

1. Direction of the Parabola (Curve Opening)

Since a=3a = 3, and it is positive, the parabola opens upward.

2. Vertex of the Parabola

The x-coordinate of the vertex is given by the formula: xvertex=b2a=52(3)=56.x_{\text{vertex}} = \frac{-b}{2a} = \frac{-5}{2(3)} = \frac{-5}{6}. Since xvertex=56x_{\text{vertex}} = -\frac{5}{6}, the vertex is on the left side of the y-axis.

3. Y-intercept

The y-intercept is the value of yy when x=0x = 0, which is: y=3(0)2+5(0)+1=1.y = 3(0)^2 + 5(0) + 1 = 1. Thus, the graph crosses the y-axis at y=1y = 1.

4. X-intercepts

To find the x-intercepts (where the graph crosses the x-axis), solve the quadratic equation: 3x2+5x+1=0.3x^2 + 5x + 1 = 0. Using the quadratic formula: x=b±b24ac2a=5±524(3)(1)2(3)=5±25126=5±136.x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} = \frac{-5 \pm \sqrt{5^2 - 4(3)(1)}}{2(3)} = \frac{-5 \pm \sqrt{25 - 12}}{6} = \frac{-5 \pm \sqrt{13}}{6}. Since the discriminant (13\sqrt{13}) is positive, there are two distinct real roots, meaning the graph intersects the x-axis at two distinct points.

Summary of the Characteristics:

  • The vertex is to the left of the y-axis (i.e., "Titik puncak di kiri sumbu Y").
  • The parabola opens upward.
  • The graph crosses the x-axis at two distinct points.
  • The graph crosses the y-axis above the x-axis (i.e., at y=1y = 1).

Correct Answers:

  • Titik puncak di kanan sumbu Y. (False, it's on the left.)
  • Kurva terbuka menghadap ke atas. (True, it opens upward.)
  • Memotong sumbu Y di bawah sumbu X. (False, it intersects at y=1y = 1, which is above the x-axis.)
  • Memotong sumbu X di dua titik berbeda. (True, it has two distinct x-intercepts.)

Would you like further details or explanations?

Related Questions:

  1. How do you determine if a parabola opens upward or downward?
  2. How do you find the vertex of a quadratic function?
  3. What does the discriminant of a quadratic equation indicate?
  4. How can you tell if a parabola will intersect the x-axis at two points, one point, or not at all?
  5. What is the significance of the y-intercept in a quadratic graph?

Tip:

The discriminant (b24acb^2 - 4ac) is key to determining the number of x-intercepts in a quadratic function.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Functions
Graph Analysis

Formulas

Quadratic Equation: y = ax^2 + bx + c
Vertex Formula: x = -b/(2a)
Discriminant: b^2 - 4ac

Theorems

Quadratic Formula
Properties of Parabolas

Suitable Grade Level

Grades 9-11