Equation in slope-intercept form that contains (4,1) and (-2,-1)

Y = mx + b ;

Then, 1 = 4m + b and -1 = -2m + b ;
b = 1 - 4m ;
-1 = -2m + ( 1 - 4m ) ;
-1 = -2m + 1 - 4m;
-1 - 1 = -6m;
-2 = -6m ;
m = ( -2 ) / ( - 6 );
m = 1 / 3 ;
b = 1 - 4 * ( 1 / 3 ) ;
b = 1 - 4 / 3;
b = - 1 / 3 ;
y = ( 1 / 3 )x - 1 / 3 ;

Ibelieve 4mn because it’s like you’re combining them