a graph shows two points, (0,8) and (3,20) Colin charges a flat fee for babysitting plus an hourly fee. His total cost is represented on the graph. How can you represent this situation algebraically

y= ?x +?

1 answer

To represent Colin's babysitting cost situation algebraically in the form \( y = mx + b \) (where \( m \) is the slope and \( b \) is the y-intercept), we can follow these steps:

  1. Identify the points given: (0, 8) and (3, 20).

    • The first point (0, 8) suggests that when no hours are worked (x = 0), the total cost (y) is 8. This is the flat fee.
    • The second point (3, 20) suggests that after working for 3 hours, the total cost is 20.
  2. Calculate the slope (m):

    • The slope formula is \( m = \frac{y_2 - y_1}{x_2 - x_1} \): \[ m = \frac{20 - 8}{3 - 0} = \frac{12}{3} = 4 \]
  3. Identify the y-intercept (b):

    • From the point (0, 8), we see that the y-intercept is \( b = 8 \).
  4. Construct the equation:

    • Now we can plug in the values into the linear equation format: \[ y = 4x + 8 \]

So, Colin's total cost for babysitting can be represented algebraically as:

\[ y = 4x + 8 \]

where \( x \) represents the number of hours babysat and \( y \) represents the total cost.