Math Problem Statement

if f(x) is a linear function f(-4)=3 and f(5)=-5, find an equation for f(x).

Solution

To find the equation of the linear function f(x)f(x), we can use the general form of a linear function:

f(x)=mx+bf(x) = mx + b

where mm is the slope and bb is the y-intercept. Given the points (4,3)(-4, 3) and (5,5)(5, -5), we can determine the slope mm using the formula:

m=y2y1x2x1m = \frac{y_2 - y_1}{x_2 - x_1}

Substitute the given points into the formula:

m=535(4)=535+4=89=89m = \frac{-5 - 3}{5 - (-4)} = \frac{-5 - 3}{5 + 4} = \frac{-8}{9} = -\frac{8}{9}

Now that we have the slope m=89m = -\frac{8}{9}, we can use one of the points to find the y-intercept bb. Let's use the point (4,3)(-4, 3):

f(x)=89x+bf(x) = -\frac{8}{9}x + b

Substitute x=4x = -4 and f(4)=3f(-4) = 3:

3=89(4)+b3 = -\frac{8}{9}(-4) + b

3=329+b3 = \frac{32}{9} + b

To isolate bb, subtract 329\frac{32}{9} from both sides:

3329=b3 - \frac{32}{9} = b

Convert 3 to a fraction with a denominator of 9:

3=2793 = \frac{27}{9}

So,

279329=b\frac{27}{9} - \frac{32}{9} = b

b=27329b = \frac{27 - 32}{9}

b=59b = -\frac{5}{9}

Therefore, the equation of the linear function is:

f(x)=89x59f(x) = -\frac{8}{9}x - \frac{5}{9}

Would you like any further details or have any questions about this solution?

Here are 5 questions you might ask next:

  1. How do I find the slope of a line from two points?
  2. Can you explain how to convert a decimal to a fraction?
  3. What is the significance of the y-intercept in a linear function?
  4. How do you graph a linear function given its equation?
  5. Can you show me how to solve a system of linear equations?

Tip: When solving for the y-intercept bb in a linear equation, always substitute one of the given points into the equation after determining the slope to solve for bb accurately.

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Math Problem Analysis

Mathematical Concepts

Linear Functions
Slope
Y-intercept
Equation of a Line

Formulas

Slope formula
Linear function equation

Theorems

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Suitable Grade Level

Grades 7-9