Math Problem Statement

The function g(x) = x^2 + 3px + (14p - 3), where p is an integer, has two equal roots. a) Find the value of p. b) For this value of p, solve the equation x^2 + 3px + (14p - 3) = 0.

Solution

The given function is:

g(x)=x2+3px+(14p3)g(x) = x^2 + 3px + (14p - 3)

It is stated that the quadratic equation has two equal roots, meaning that the discriminant of the quadratic must be zero. For a quadratic equation of the form ax2+bx+c=0ax^2 + bx + c = 0, the discriminant Δ\Delta is given by:

Δ=b24ac\Delta = b^2 - 4ac

For the given quadratic:

  • a=1a = 1
  • b=3pb = 3p
  • c=14p3c = 14p - 3

Part (a): Finding the value of pp

The discriminant must equal zero for the quadratic to have two equal roots:

Δ=(3p)24(1)(14p3)=0\Delta = (3p)^2 - 4(1)(14p - 3) = 0

Simplifying this:

9p24(14p3)=09p^2 - 4(14p - 3) = 0

9p256p+12=09p^2 - 56p + 12 = 0

This is a quadratic equation in pp. Let's solve it using the quadratic formula:

p=(56)±(56)24(9)(12)2(9)p = \frac{-(-56) \pm \sqrt{(-56)^2 - 4(9)(12)}}{2(9)}

p=56±313643218p = \frac{56 \pm \sqrt{3136 - 432}}{18}

p=56±270418p = \frac{56 \pm \sqrt{2704}}{18}

p=56±5218p = \frac{56 \pm 52}{18}

Now, solving for pp:

  1. p=56+5218=10818=6p = \frac{56 + 52}{18} = \frac{108}{18} = 6
  2. p=565218=418=29p = \frac{56 - 52}{18} = \frac{4}{18} = \frac{2}{9}

Since pp is stated to be an integer, the only valid solution is:

p=6p = 6

Part (b): Solving the quadratic equation for p=6p = 6

Substitute p=6p = 6 into the equation x2+3px+(14p3)=0x^2 + 3px + (14p - 3) = 0:

x2+3(6)x+(14(6)3)=0x^2 + 3(6)x + (14(6) - 3) = 0

x2+18x+(843)=0x^2 + 18x + (84 - 3) = 0

x2+18x+81=0x^2 + 18x + 81 = 0

This simplifies to:

(x+9)2=0(x + 9)^2 = 0

Thus, the solution is:

x=9x = -9

Let me know if you'd like further details or have any questions!

Follow-up questions:

  1. What are the implications of having two equal roots in a quadratic equation?
  2. How is the discriminant used to determine the nature of the roots of a quadratic equation?
  3. Can the quadratic formula be applied if the discriminant is negative? What does this imply about the roots?
  4. What are the different forms of a quadratic equation, and how do they help in solving it?
  5. How can you check if the solution x=9x = -9 is correct by substituting it back into the original equation?

Tip: Always check if an equation can be factored easily before applying the quadratic formula.

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Math Problem Analysis

Mathematical Concepts

Quadratic Equations
Discriminant
Algebra

Formulas

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

Theorems

Discriminant Theorem
Quadratic Formula

Suitable Grade Level

Grades 9-12