A linear demand function has a slope of [tex]-\frac{1}{2}[/tex]. The price is \$50 per unit when the quantity demanded is 10 units.

1. Find the demand function.
2. Find the intercepts on both axes.
3. What is the price if the quantity demanded is 20 units?



Answer :

To find the demand function, we start with the information given. We know that the slope of the demand function is [tex]\(-\frac{1}{2}\)[/tex] and we have a specific point on this line: when the quantity demanded is 10 units, the price is [tex]$50. ### Step 1: Calculate the Y-Intercept (Price Intercept) The general form of the linear equation is: \[ \text{price} = \text{slope} \times \text{quantity} + \text{intercept} \] Given the slope \( -\frac{1}{2} \) and a point \((10, 50)\), we can substitute these values into the equation to find the intercept. \[ 50 = -\frac{1}{2} \times 10 + \text{intercept} \] Simplifying, we get: \[ 50 = -5 + \text{intercept} \] Adding 5 to both sides to solve for the intercept: \[ \text{intercept} = 50 + 5 = 55 \] So, the y-intercept of the demand function is 55. ### Step 2: Form the Demand Function Now that we know the slope and the y-intercept, we can write the demand function as: \[ \text{price} = -\frac{1}{2} \times \text{quantity} + 55 \] ### Step 3: Calculate the X-Intercept (Quantity Intercept) The x-intercept occurs where the price is 0. We set the price to 0 in the demand function and solve for the quantity. \[ 0 = -\frac{1}{2} \times \text{quantity} + 55 \] Multiplying through by 2 to clear the fraction: \[ 0 = -1 \times \text{quantity} + 110 \] Solving for the quantity: \[ \text{quantity} = 110 \] So, the x-intercept of the demand function is 110. ### Step 4: Calculate the Price at a Quantity of 50 Units We use the demand function to find the price when the quantity demanded is 50 units. \[ \text{price} = -\frac{1}{2} \times 50 + 55 \] Simplifying, we get: \[ \text{price} = -25 + 55 = 30 \] So, the price when the quantity demanded is 50 units is $[/tex]30.

### Summary
- The y-intercept (price intercept) is [tex]\( \$55 \)[/tex].
- The x-intercept (quantity intercept) is [tex]\( 110 \)[/tex] units.
- The price when the quantity demanded is 50 units is [tex]\( \$30 \)[/tex].

Hence, the demand function is:
[tex]\[ \text{price} = -\frac{1}{2} \times \text{quantity} + 55 \][/tex]

These intercepts and the price at 50 units demonstrate the linear relationship described by the demand function.