# Math Help - line joining

1. ## line joining

what is the line joining (-4,1) and (-2,5)

2. Originally Posted by alysha230893
what is the line joining (-4,1) and (-2,5)
Here you have

$(x_1, y_1) = (-4, 1)$

and

$(x_2, y_2) = (-2, 5)$.

The equation of the line is

$y - y_1 = m(x - x_1)$, where $m = \frac{y_2 - y_1}{x_2 - x_1}$.

3. Firstly, you need to find the gradient, in the form

y=mx+c

(y1-y2)/(x1-x2)

so

(5-1)/(-2--4) = 4/2 = 2

So you know that the line is y=2x+c

Now substitute one of the points into the equation

1=2(-4)+c

1=-8+c

so 9 = c

So the equation of the line is

y=2x+9