吴恩达deeplearning.ai课程中序列模型这一章的作业Rnn（lstm）反向传播推导

Question

为什么自己算的结果和答案中给的结果对不上？
for t in reversed(range(T_x)):
# Compute all gradients using lstm_cell_backward
gradients = lstm_cell_backward(da[:, :, t] + da_prevt, dc_prevt, caches[t])
# Store or add the gradient to the parameters' previous step's gradient
da_prevt = gradients['da_prev']
dc_prevt = gradients['dc_prev']
dx[:,:,t] = gradients['dxt']
dWf = dWf + gradients['dWf']
dWi = dWi + gradients['dWi']
dWc = dWc + gradients['dWc']
dWo = dWo + gradients['dWo']
dbf = dbf + gradients['dbf']
dbi = dbi + gradients['dbi']
dbc = dbc + gradients['dbc']
dbo = dbo + gradients['dbo']

            这个对吗da[:, :, t] + da_prevt, dc_prevt