y +3 = (1/4)(x +3)
The two-point form of the equation for a line is good for this.
... y -y1 = (y2-y1)/(x2-x1)(x -x1)
Substituting your values, we have ...
... y -(-3) = (-1-(-3))/(5-(-3))(x -(-3))
... y +3 = 2/8(x +3)
Since you ask for "an equation," we can leave it in this form.
... y +3 = (1/4)(x +3)
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Or we can rearrange it to slope-intercept form:
... y = (1/4)x -(2 1/4)
or put it in standard form:
... x -4y = 9
