Differentiate : (t^3 +2t -1) / (t+1) =

I don't understand how the answer is: (1)(t^3+2t-1) - (3t^2 +2)(t+1) All over (t+1)^2

bottom * derivative of top - top * derivative of bottom

all over bottom squared
[(t+1)(3t^2 + 2) - (t^3+2t-1)(1) ] / (t+1)^2

I disagree with your signs