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

y=mx+c

The formula for gradient is

(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