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Question

What is the equation of line through (1,2) and (3,8)

This question was previously asked in
SSC CGL 2025 Tier 1 Question Paper (25-Sep-2025) (Shift 3)
The correct answer is
$y = 3x - 1$

Finding the Equation of a Line

To find the equation of a line passing through two points, $(x_1, y_1)$ and $(x_2, y_2)$, we first determine the slope ($m$) and then the y-intercept ($c$) to form the equation $y = mx + c$. The given points are (1, 2) and (3, 8).

1. Calculate the Slope ($m$)

The slope is calculated using the formula:

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

Substitute the coordinates of the given points:

$m = \frac{8 - 2}{3 - 1} = \frac{6}{2} = 3$

The slope ($m$) is 3.

2. Determine the Y-intercept ($c$)

Use the slope ($m=3$) and one of the points (e.g., (1, 2)) in the slope-intercept form ($y = mx + c$):

$2 = 3(1) + c$

$2 = 3 + c$

Solve for $c$:

$c = 2 - 3 = -1$

The y-intercept ($c$) is -1.

3. Write the Equation

Substitute the calculated slope ($m=3$) and y-intercept ($c=-1$) into the slope-intercept form $y = mx + c$:

$y = 3x - 1$

This is the equation of the line passing through the points (1, 2) and (3, 8).

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