I don't understand the equation that you get from combining the two linear perceptrons is non-linear?
The video starts with two linear perceptrons with the equations: $$e1 = 5x_1 -2x_2 - 8 = 0 \hspace{10ex} e2 = 7x_1 - 3x_2 + 1 = 0 $$
Note: The bias unit signs flip between the written equation and the neural network diagram. I am using the negative sign since it is continued throughout the rest of the video
Then we go on to combine them with respective weights and biases as follows: $$ 7e_1 + 5e_2 -6 = 0$$ When I do the math, I get: $$ 7e_1 + 5e_2 - 6 = 0 $$ $$ 7(5x_1 -2x_2 - 8) + 5(7x_1 - 3x_2 + 1) - 6 = 0$$ $$ 35x_1 - 14x_2 - 56 + 35x_1 -15x_2 +5 -6 = 0$$ $$ 70x_1 - 29x_2 - 57 = 0$$
The resulting equation is very much linear, however, the idea is that that this generates a non-linear equation (and model).
What am I doing incorrectly in the way I am combining the two models?