If the supply function for XT-tires is [tex] p = q^2 + 8q - 458 [/tex], where [tex] p [/tex] is the price that corresponds to quantity [tex] q [/tex], and the demand function is [tex] p = -6q^2 + 5q + 2126 [/tex], find the market equilibrium point.

Market equilibrium point, [tex] (q, p) [/tex]: [tex] \square [/tex]



Answer :

To find the market equilibrium point, we need to determine the quantity [tex]\( q \)[/tex] and price [tex]\( p \)[/tex] where the supply function equals the demand function.

Let's start with the given supply and demand functions:
- Supply function: [tex]\( p = q^2 + 8q - 458 \)[/tex]
- Demand function: [tex]\( p = -6q^2 + 5q + 2126 \)[/tex]

### Step 1: Set the supply function equal to the demand function

To find the equilibrium quantity, equate the supply function to the demand function:
[tex]\[ q^2 + 8q - 458 = -6q^2 + 5q + 2126 \][/tex]

### Step 2: Combine like terms

Move all terms to one side of the equation to set it equal to zero:
[tex]\[ q^2 + 8q - 458 + 6q^2 - 5q - 2126 = 0 \][/tex]
Simplify the equation by combining like terms:
[tex]\[ (q^2 + 6q^2) + (8q - 5q) + (-458 - 2126) = 0 \][/tex]
[tex]\[ 7q^2 + 3q - 2584 = 0 \][/tex]

### Step 3: Solve the quadratic equation for [tex]\( q \)[/tex]

We need to solve the quadratic equation:
[tex]\[ 7q^2 + 3q - 2584 = 0 \][/tex]

The solutions to this quadratic equation are:
[tex]\[ q = \frac{-136}{7} \, \text{or} \, q = \frac{--2584}{7}\][/tex]

Select the physically meaningful solution which is [tex]\( q = \frac{-136}{7} \)[/tex].

### Step 4: Substitute the equilibrium quantity [tex]\( q \)[/tex] back into the supply or demand function to find the equilibrium price

Substitute [tex]\( q = -\frac{136}{7} \)[/tex] into either the supply or demand function. Let's use the supply function [tex]\( p = q^2 + 8q - 458 \)[/tex]:

[tex]\[ p = \left(-\frac{136}{7}\right)^2 + 8\left(-\frac{136}{7}\right) - 458 \][/tex]

Simplified, this gives us:
[tex]\[ p = \frac{-11562}{49} \][/tex]

### Result

The market equilibrium point [tex]\((q, p)\)[/tex] is:
[tex]\[ \left( -\frac{136}{7}, -\frac{11562}{49} \right) \][/tex]