multiline equation with indentation control

I have a following multiline equation,

$$\label{eq:19} \begin{split} I_{1\to 1}(2)&=\tanh\Big(w^{ro}_{1,1}\cdot{h_1}^{x_1}(2) + w^{ro}_{2,1}\cdot{h_2}^{x_1}(2)+ w^{io}_{1,1}\cdot{x}_{1}(2)\Big) \\ &=\tanh\bigg(w^{ro}_{1,1}\cdot \Big( (1-\alpha) \cdot \alpha \cdot h_1^{x_1}(1) + \alpha \cdot \tanh \Big(w^{rr}_{1,1}\cdot h_1^{x_1}(1) + w^{rr}_{2,1}\cdot h_2^{x_1}(1) + w^{ir}_{1,1}\cdot x_1(2)\Big)\Big) \\ &+ w^{ro}_{2,1} \cdot \Big((1-\alpha) \cdot \alpha \cdot h_2^{x_1}(1) + \alpha \cdot \tanh \Big(w^{rr}_{1,2}\cdot h_1^{x_1}(1) + w^{rr}_{2,2}\cdot h_2^{x_1}(1) + w^{ir}_{1,2}\cdot x_1(2)\Big)\Big) \\ &+ w^{io}_{1,1}\cdot{x}_{1}(2) \bigg). \end{split}$$


I would like the last two lines starting with '+' to be shifted couple spaces to the right for better visual. Any help will be greatly appreciated!

• unrelated but always use \bigl(\bigr) not \big(\big) and avoid numbers in \label – David Carlisle Jun 7 at 20:40

\documentclass[a4paper,landscape]{article}
\usepackage{geometry}
\usepackage{amsmath}

\begin{document}

$$\label{eq:dontusenumbers-quad} \begin{split} I_{1\to 1}(2)&=\tanh\Bigl(w^{ro}_{1,1}\cdot{h_1}^{x_1}(2) + w^{ro}_{2,1}\cdot{h_2}^{x_1}(2)+ w^{io}_{1,1}\cdot{x}_{1}(2)\Bigr) \\ &=\tanh\biggl(w^{ro}_{1,1}\cdot \Bigl( (1-\alpha) \cdot \alpha \cdot h_1^{x_1}(1) + \alpha \cdot \tanh \Bigl(w^{rr}_{1,1}\cdot h_1^{x_1}(1) + w^{rr}_{2,1}\cdot h_2^{x_1}(1) + w^{ir}_{1,1}\cdot x_1(2)\Bigr)\Bigr) \\ &\qquad+ w^{ro}_{2,1} \cdot \Bigl((1-\alpha) \cdot \alpha \cdot h_2^{x_1}(1) + \alpha \cdot \tanh \Bigl(w^{rr}_{1,2}\cdot h_1^{x_1}(1) + w^{rr}_{2,2}\cdot h_2^{x_1}(1) + w^{ir}_{1,2}\cdot x_1(2)\Bigr)\Bigr) \\ &\qquad+ w^{io}_{1,1}\cdot{x}_{1}(2) \biggr). \end{split}$$
\label{eq:dontusenumbers-aligned} \begin{split} I_{1\to 1}(2)&=\tanh\Bigl(w^{ro}_{1,1}\cdot{h_1}^{x_1}(2) + w^{ro}_{2,1}\cdot{h_2}^{x_1}(2)+ w^{io}_{1,1}\cdot{x}_{1}(2)\Bigr) \\ &= \begin{aligned}[t] \tanh\biggl(&w^{ro}_{1,1}\cdot \Bigl( (1-\alpha) \cdot \alpha \cdot h_1^{x_1}(1) + \alpha \cdot \tanh \Bigl(w^{rr}_{1,1}\cdot h_1^{x_1}(1) + w^{rr}_{2,1}\cdot h_2^{x_1}(1) + w^{ir}_{1,1}\cdot x_1(2)\Bigr)\Bigr) \\ &+ w^{ro}_{2,1} \cdot \Bigl((1-\alpha) \cdot \alpha \cdot h_2^{x_1}(1) + \alpha \cdot \tanh \Big(w^{rr}_{1,2}\cdot h_1^{x_1}(1) + w^{rr}_{2,2}\cdot h_2^{x_1}(1) + w^{ir}_{1,2}\cdot x_1(2)\Bigr)\Bigr) \\ &+ w^{io}_{1,1}\cdot{x}_{1}(2) \biggr). \end{aligned} \end{split}