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JAMB Mathematics 2012 Paper

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Question : 27

Total: 48

Find the equation of the line through the points (-2, 1) and (-

\frac{1}{2}

, 4)

y = 2x - 3
y = 2x + 5
y = 3x - 2
y = 2x + 1

Solution:

Concept:

Use the two-point form of a straight line to find its equation.

Explanation:

Let

(x_1, y_1) = (-2, 1)

and

(x_2, y_2) = \left(-\frac{1}{2}, 4\right)

.

The slope

m

is given by

\frac{y_2 - y_1}{x_2 - x_1}

.

So,

m = \frac{4 - 1}{-\frac{1}{2} - (-2)} = \frac{3}{\frac{3}{2}} = 2

.

Using

y - y_1 = m(x - x_1)

:

y - 1 = 2(x - (-2))

y - 1 = 2x + 4

y = 2x + 5

.

Answer:

The equation of the line is

y = 2x + 5

, which is option B.

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