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Chin was shown the graph of a line that contained the point [tex]\((1,7)\)[/tex]. He wrote [tex]\( f(x) = 4x + 3 \)[/tex] to correctly represent the line. Which of these equations could represent the same line?

A. [tex]\( y - 7 = 3(x - 1) \)[/tex]
B. [tex]\( y - 1 = 3(x - 7) \)[/tex]
C. [tex]\( y - 7 = 4(x - 1) \)[/tex]
D. [tex]\( y - 1 = 4(x - 7) \)[/tex]


Sagot :

Let's analyze each of the given equations to determine if they could represent the line [tex]\( f(x) = 4x + 3 \)[/tex] that passes through the point [tex]\((1,7)\)[/tex].

### 1. Equation: [tex]\( y - 7 = 3(x - 1) \)[/tex]

First, we need to rewrite this equation in slope-intercept form ([tex]\( y = mx + b \)[/tex]):

1. Distribute the 3 on the right-hand side:
[tex]\[ y - 7 = 3(x - 1) \\ y - 7 = 3x - 3 \][/tex]
2. Add 7 to both sides to isolate [tex]\( y \)[/tex]:
[tex]\[ y = 3x - 3 + 7 \\ y = 3x + 4 \][/tex]

The slope ([tex]\( m \)[/tex]) is 3 and the y-intercept is 4. This does not match our original line equation [tex]\( f(x) = 4x + 3 \)[/tex]. So, the first equation does not represent the same line.

### 2. Equation: [tex]\( y - 1 = 3(x - 7) \)[/tex]

Next, we transform this equation to slope-intercept form:

1. Distribute the 3 on the right-hand side:
[tex]\[ y - 1 = 3(x - 7) \\ y - 1 = 3x - 21 \][/tex]
2. Add 1 to both sides to isolate [tex]\( y \)[/tex]:
[tex]\[ y = 3x - 21 + 1 \\ y = 3x - 20 \][/tex]

The slope ([tex]\( m \)[/tex]) here is 3 and the y-intercept is -20. This also does not match our original line equation. Thus, the second equation does not represent the same line.

### 3. Equation: [tex]\( y - 7 = 4(x - 1) \)[/tex]

Let’s rewrite this equation in slope-intercept form:

1. Distribute the 4 on the right-hand side:
[tex]\[ y - 7 = 4(x - 1) \\ y - 7 = 4x - 4 \][/tex]
2. Add 7 to both sides to isolate [tex]\( y \)[/tex]:
[tex]\[ y = 4x - 4 + 7 \\ y = 4x + 3 \][/tex]

The slope ([tex]\( m \)[/tex]) here is 4 and the y-intercept is 3. This matches our original line equation [tex]\( f(x) = 4x + 3 \)[/tex]. Therefore, the third equation represents the same line.

### 4. Equation: [tex]\( y - 1 = 4(x - 7) \)[/tex]

Finally, transform this to slope-intercept form:

1. Distribute the 4 on the right-hand side:
[tex]\[ y - 1 = 4(x - 7) \\ y - 1 = 4x - 28 \][/tex]
2. Add 1 to both sides to isolate [tex]\( y \)[/tex]:
[tex]\[ y = 4x - 28 + 1 \\ y = 4x - 27 \][/tex]

The slope ([tex]\( m \)[/tex]) is 4 but the y-intercept is -27. This does not match our original line's intercept. Thus, the fourth equation does not represent the same line.

### Conclusion
Out of the four given equations, only [tex]\( y - 7 = 4(x - 1) \)[/tex] represents the same line as [tex]\( f(x) = 4x + 3 \)[/tex].