what is the default activation function of dense layer in keras

Question

i read the documintation for keras, and i found that when we ignore the activation function it will be just a simple linear function

activation: Activation function to use. If you don't specify anything, no activation is applied (ie. "linear" activation: a(x) = x).

but also by default the bias is True, and I try this example, and it solved my problem and gave me the correct weight:

So what actually the default activation function here, and how can I detect it?

Thanks

Answer 1

If you don't specify an activation function, the value of a neuron will just be a weighted sum of inputs and biases. Applying an activation function happens after the sum is calculated so if you don't specify any, it will simply remain like that.