Let [tex]f(x) = mx + c[/tex], where [tex]m[/tex] and [tex]c[/tex] are constants. If [tex]f(3) = 4[/tex] and [tex]f(6) = -2[/tex], find the values of [tex]m[/tex] and [tex]c[/tex], and also find [tex]f(n)[/tex].



Answer :

To solve this problem, we are dealing with the linear equation of the form [tex]\( f(x) = mx + c \)[/tex]. We need to determine the values of [tex]\( m \)[/tex] and [tex]\( c \)[/tex] given two points on the line: [tex]\( (3, 4) \)[/tex] and [tex]\( (6, -2) \)[/tex]. Additionally, we need to find the value of [tex]\( mac \)[/tex] and [tex]\( f(n) \)[/tex].

### Step-by-Step Solution

1. Set up the equations:

Since [tex]\( f(x) = mx + c \)[/tex], we substitute the given points into the equation.

For the point [tex]\( (3, 4) \)[/tex]:
[tex]\[ 4 = 3m + c \][/tex]

For the point [tex]\( (6, -2) \)[/tex]:
[tex]\[ -2 = 6m + c \][/tex]

2. Form the system of equations:

We have two equations:
[tex]\[ \begin{cases} 4 = 3m + c & \quad \text{(Equation 1)} \\ -2 = 6m + c & \quad \text{(Equation 2)} \end{cases} \][/tex]

3. Solve the system of equations:

Subtract Equation 1 from Equation 2 to eliminate [tex]\( c \)[/tex]:
[tex]\[ (-2) - 4 = (6m + c) - (3m + c) \][/tex]
Simplify:
[tex]\[ -6 = 3m \][/tex]
Solving for [tex]\( m \)[/tex]:
[tex]\[ m = -2 \][/tex]

4. Find [tex]\( c \)[/tex]:

Substitute [tex]\( m = -2 \)[/tex] back into Equation 1:
[tex]\[ 4 = 3(-2) + c \][/tex]
Simplify:
[tex]\[ 4 = -6 + c \][/tex]
Solving for [tex]\( c \)[/tex]:
[tex]\[ c = 10 \][/tex]

5. Calculate [tex]\( mac \)[/tex]:

Given that [tex]\( m = -2 \)[/tex] and [tex]\( c = 10 \)[/tex]:
[tex]\[ mac = m \cdot a \cdot c \][/tex]
Assuming [tex]\( a = 1 \)[/tex] for simplicity as typical problems set [tex]\( a = 1 \)[/tex] if not specified otherwise, we get:
[tex]\[ mac = (-2) \cdot 1 \cdot 10 = -20 \][/tex]

6. Find [tex]\( f(n) \)[/tex]:

The function [tex]\( f(x) \)[/tex] is now completely determined:
[tex]\[ f(x) = -2x + 10 \][/tex]

To find [tex]\( f(n) \)[/tex]:
[tex]\[ f(n) = -2n + 10 \][/tex]

### Summary of Results

- [tex]\( m = -2 \)[/tex]
- [tex]\( c = 10 \)[/tex]
- [tex]\( mac = -20 \)[/tex]
- [tex]\( f(n) = -2n + 10 \)[/tex]

Therefore, the value of [tex]\( mac \)[/tex] is [tex]\( -20 \)[/tex], and the function [tex]\( f(n) \)[/tex] simplifies to [tex]\( f(n) = -2n + 10 \)[/tex].