Math Problem Statement

Substitute the values for ab, and c into b2 – 4ac to determine the discriminant. Which quadratic equations will have two real number solutions? (The related quadratic function will have two x-intercepts.) Check all that apply. 

0 = 2x2 – 7x – 9

0 = x2 – 4x + 4

0 = 4x2 – 3x – 1

0 = x2 – 2x – 8

0 = 3x2 + 5x + 3

Solution

To determine which quadratic equations will have two real solutions, we need to calculate the discriminant (Δ\Delta) for each equation. The discriminant formula is:

Δ=b24ac\Delta = b^2 - 4ac

  • If Δ>0\Delta > 0, the quadratic equation has two real and distinct solutions (or two xx-intercepts).
  • If Δ=0\Delta = 0, the quadratic equation has one real solution (or one xx-intercept).
  • If Δ<0\Delta < 0, the quadratic equation has no real solutions (no xx-intercepts).

Now, let's calculate the discriminant for each equation.


1. 0=2x27x90 = 2x^2 - 7x - 9

Here, a=2a = 2, b=7b = -7, and c=9c = -9.

Δ=(7)24(2)(9)=49+72=121\Delta = (-7)^2 - 4(2)(-9) = 49 + 72 = 121

Since Δ=121>0\Delta = 121 > 0, this equation has two real solutions.


2. 0=x24x+40 = x^2 - 4x + 4

Here, a=1a = 1, b=4b = -4, and c=4c = 4.

Δ=(4)24(1)(4)=1616=0\Delta = (-4)^2 - 4(1)(4) = 16 - 16 = 0

Since Δ=0\Delta = 0, this equation has one real solution.


3. 0=4x23x10 = 4x^2 - 3x - 1

Here, a=4a = 4, b=3b = -3, and c=1c = -1.

Δ=(3)24(4)(1)=9+16=25\Delta = (-3)^2 - 4(4)(-1) = 9 + 16 = 25

Since Δ=25>0\Delta = 25 > 0, this equation has two real solutions.


4. 0=x22x80 = x^2 - 2x - 8

Here, a=1a = 1, b=2b = -2, and c=8c = -8.

Δ=(2)24(1)(8)=4+32=36\Delta = (-2)^2 - 4(1)(-8) = 4 + 32 = 36

Since Δ=36>0\Delta = 36 > 0, this equation has two real solutions.


5. 0=3x2+5x+30 = 3x^2 + 5x + 3

Here, a=3a = 3, b=5b = 5, and c=3c = 3.

Δ=(5)24(3)(3)=2536=11\Delta = (5)^2 - 4(3)(3) = 25 - 36 = -11

Since Δ=11<0\Delta = -11 < 0, this equation has no real solutions.


Summary:

The quadratic equations with two real solutions are:

  • 0=2x27x90 = 2x^2 - 7x - 9
  • 0=4x23x10 = 4x^2 - 3x - 1
  • 0=x22x80 = x^2 - 2x - 8

Would you like more details or clarifications?


Here are 5 related questions:

  1. What happens if the discriminant is negative in a quadratic equation?
  2. How can the quadratic formula be used to find real solutions?
  3. How does the graph of a quadratic equation relate to its discriminant?
  4. Can a quadratic equation with a discriminant of zero have complex solutions?
  5. What is the relationship between the coefficients and the shape of the parabola?

Tip: The discriminant not only tells the number of solutions but also helps determine the nature of the solutions—whether they are real or complex.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Discriminant
Real Solutions

Formulas

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

Theorems

Discriminant Theorem: Determines the number and nature of the solutions based on the value of the discriminant.

Suitable Grade Level

Grades 8-10