Math Problem Statement

The table of values represents a linear function g(x), where x is the number of days that have passed and g(x) is the balance in the bank account:

xg(x)

0

$325

5

$400

10

$475

Part A: Find and interpret the slope of the function. (3 points)

Part B: Write the equation of the line in point-slope, slope-intercept, and standard forms. (3 points)

Part C: Write the equation of the line using function notation. (2 points)

Part D: What is the balance in the bank account after 12 days? (2 points)

Solution

Let's break this down step by step:

Part A: Find and interpret the slope of the function. (3 points)

The slope of a linear function represents the rate of change of the dependent variable (in this case, the bank balance g(x)g(x)) with respect to the independent variable xx (the number of days).

The formula for the slope mm is:

m=ΔyΔx=g(x2)g(x1)x2x1m = \frac{\Delta y}{\Delta x} = \frac{g(x_2) - g(x_1)}{x_2 - x_1}

Using the two points from the table:

  • (x1,g(x1))=(0,325)(x_1, g(x_1)) = (0, 325)
  • (x2,g(x2))=(5,400)(x_2, g(x_2)) = (5, 400)

Substitute into the slope formula:

m=40032550=755=15m = \frac{400 - 325}{5 - 0} = \frac{75}{5} = 15

Interpretation:
The slope is 15, which means the balance in the bank account increases by $15 per day.

Part B: Write the equation of the line in point-slope, slope-intercept, and standard forms. (3 points)

  1. Point-slope form:
    The point-slope form of a line is:

    yy1=m(xx1)y - y_1 = m(x - x_1)

    Using the slope m=15m = 15 and the point (0,325)(0, 325):

    g(x)325=15(x0)g(x) - 325 = 15(x - 0)

    Simplified:

    g(x)325=15xg(x) - 325 = 15x

  2. Slope-intercept form:
    The slope-intercept form of a line is:

    g(x)=mx+bg(x) = mx + b

    From the slope m=15m = 15 and the initial value g(0)=325g(0) = 325, the equation is:

    g(x)=15x+325g(x) = 15x + 325

  3. Standard form:
    The standard form of a line is:

    Ax+By=CAx + By = C

    Rearranging the slope-intercept form g(x)=15x+325g(x) = 15x + 325:

    15xg(x)=32515x - g(x) = -325

    Multiplying through by -1:

    15x+g(x)=325-15x + g(x) = 325

    Or:

    15xg(x)=32515x - g(x) = -325

Part C: Write the equation of the line using function notation. (2 points)

In function notation, the equation is simply:

g(x)=15x+325g(x) = 15x + 325

This represents the same linear equation as in Part B but written explicitly as a function.

Part D: What is the balance in the bank account after 12 days? (2 points)

To find the balance after 12 days, substitute x=12x = 12 into the equation:

g(12)=15(12)+325=180+325=505g(12) = 15(12) + 325 = 180 + 325 = 505

So, the balance after 12 days is $505.


Would you like any further details or clarification on any part?

5 Related Questions:

  1. How would the slope change if the bank balance decreased over time instead of increasing?
  2. What is the significance of the y-intercept in this problem?
  3. How can you use this model to predict the balance after 20 days?
  4. How do you convert between point-slope form and slope-intercept form?
  5. What happens to the equation if there was an initial fee, reducing the balance at the start?

Tip: The slope in a linear function always represents the rate of change, whether it's an increase or decrease.

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Math Problem Analysis

Mathematical Concepts

Linear Functions
Slope
Equation of a Line

Formulas

Slope formula: m = (g(x2) - g(x1)) / (x2 - x1)
Point-slope form: y - y1 = m(x - x1)
Slope-intercept form: y = mx + b
Standard form: Ax + By = C

Theorems

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Suitable Grade Level

Grades 8-10