If you follow the slope formula your answer should be -1
proof:
slope formula: Y2-Y1/X2-X1=Slope (M)
4,-1 will be our x1,y1 and -1,4 will be our x2,y2
plug in numbers into formula: 4-(-1)/ -1-4
simplify you get 5/-5
simplify again and your answer is -1!!!
If its wrong im sorry