Question 84883
FIRST WE FIND THE SLOPE 
(Y2-Y1)/(X2-X1)
(0+4)/(4-0)=4/4=1 FOR THE SLOPE.
NOW WE REPLACE X 7 Y IN THE LINE EQUATION [Y=mX+b] & SOLVE FOR (b) THE Y INTERCEPT. (WHICH WE ALREADY KNOW (0,-4)
-4=-1*0+b
-4=b  WHICH IS THE Y INTERCEPT.
THUS THE EQUATION IS
Y=1*X-4 OR Y=X-4
 {{{ graph( 300, 200, -6, 5, -10, 10, y = x -4) }}} (graph 300x200 pixels, x from -6 to 5, y from -10 to 10, y = x -4).