Math Problem Statement

the equation 4(p-2x) = (12+15p)/(x+p) where p is constant has two distinct real roots. a) show that 3p^2 - 10p - 8 > 0 b) using algebra find the range of possible values of p

Solution

Let's solve the given equation step by step.

Part (a): Show that 3p210p8>03p^2 - 10p - 8 > 0

We are given the equation: 4(p2x)=12+15px+p4(p - 2x) = \frac{12 + 15p}{x + p} where pp is a constant, and the equation has two distinct real roots. First, we will manipulate the equation to derive the necessary inequality for pp.

Step 1: Multiply both sides by x+px + p to eliminate the denominator:

4(p2x)(x+p)=12+15p4(p - 2x)(x + p) = 12 + 15p

Step 2: Expand the left-hand side:

4(p2x)(x+p)=4(p(x+p)2x(x+p))4(p - 2x)(x + p) = 4(p(x + p) - 2x(x + p)) =4(px+p22x22px)= 4(px + p^2 - 2x^2 - 2px) =4(p22x2+px2px)= 4(p^2 - 2x^2 + px - 2px) =4(p22x2px)= 4(p^2 - 2x^2 - px)

So the equation becomes: 4(p22x2px)=12+15p4(p^2 - 2x^2 - px) = 12 + 15p

Step 3: Rearrange into standard quadratic form:

Now, we focus on the xx-terms to write the equation in standard quadratic form ax2+bx+c=0ax^2 + bx + c = 0.

From the equation: 4(2x2px+p2)=12+15p4(-2x^2 - px + p^2) = 12 + 15p We can rewrite this as: 8x24px+4p2=12+15p-8x^2 - 4px + 4p^2 = 12 + 15p 8x24px+(4p215p12)=0-8x^2 - 4px + (4p^2 - 15p - 12) = 0

Thus, the quadratic in xx is: 8x24px+(4p215p12)=0-8x^2 - 4px + (4p^2 - 15p - 12) = 0 Now, the condition for two distinct real roots is that the discriminant of this quadratic must be positive. The discriminant Δ\Delta of a quadratic equation ax2+bx+c=0ax^2 + bx + c = 0 is given by: Δ=b24ac\Delta = b^2 - 4ac

Here, a=8a = -8, b=4pb = -4p, and c=4p215p12c = 4p^2 - 15p - 12.

Step 4: Calculate the discriminant:

Δ=(4p)24(8)(4p215p12)\Delta = (-4p)^2 - 4(-8)(4p^2 - 15p - 12) =16p24(8)(4p215p12)= 16p^2 - 4(-8)(4p^2 - 15p - 12) =16p2+32(4p215p12)= 16p^2 + 32(4p^2 - 15p - 12) =16p2+128p2480p384= 16p^2 + 128p^2 - 480p - 384 =144p2480p384= 144p^2 - 480p - 384

For two distinct real roots, we require the discriminant Δ>0\Delta > 0. Therefore, we need: 144p2480p384>0144p^2 - 480p - 384 > 0 Dividing the entire inequality by 48 to simplify: 3p210p8>03p^2 - 10p - 8 > 0 Thus, we have shown that 3p210p8>03p^2 - 10p - 8 > 0, which completes part (a).


Part (b): Find the range of possible values of pp

Now, we will solve the inequality 3p210p8>03p^2 - 10p - 8 > 0 to find the range of pp.

Step 1: Solve the quadratic equation 3p210p8=03p^2 - 10p - 8 = 0

We use the quadratic formula: p=(10)±(10)24(3)(8)2(3)p = \frac{-(-10) \pm \sqrt{(-10)^2 - 4(3)(-8)}}{2(3)} p=10±100+966p = \frac{10 \pm \sqrt{100 + 96}}{6} p=10±1966p = \frac{10 \pm \sqrt{196}}{6} p=10±146p = \frac{10 \pm 14}{6} So the two roots are: p=10+146=4andp=10146=23p = \frac{10 + 14}{6} = 4 \quad \text{and} \quad p = \frac{10 - 14}{6} = -\frac{2}{3}

Step 2: Analyze the inequality 3p210p8>03p^2 - 10p - 8 > 0

The quadratic inequality 3p210p8>03p^2 - 10p - 8 > 0 is satisfied when pp lies outside the roots p=23p = -\frac{2}{3} and p=4p = 4.

Thus, the solution to the inequality is: p<23orp>4p < -\frac{2}{3} \quad \text{or} \quad p > 4

Final Answer:

The range of possible values of pp is: p(,23)(4,)p \in (-\infty, -\frac{2}{3}) \cup (4, \infty)

Let me know if you'd like further details or explanations on any part of this solution!

Related Questions:

  1. How do you derive the quadratic discriminant formula?
  2. What are the properties of quadratic inequalities?
  3. What is the significance of having two distinct real roots for a quadratic equation?
  4. Can the method used here be applied to non-quadratic equations?
  5. How do different values of constants like pp affect the nature of the roots?

Tip: When solving quadratic inequalities, always check the signs of intervals around the roots to determine where the inequality holds.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Inequalities

Formulas

Quadratic discriminant formula: Δ = b^2 - 4ac
Quadratic equation formula: ax^2 + bx + c = 0
Quadratic inequality: 3p^2 - 10p - 8 > 0

Theorems

Discriminant of quadratic equations
Quadratic formula: p = [-b ± sqrt(b^2 - 4ac)] / 2a

Suitable Grade Level

Grades 10-12