railsでbootstrapをつかいたい

環境 windows10
ruby 2.6.3
rails 5.2.3
bootstrapでナビゲーションバーを作りたいのですが以下のエラーが出てしまいます、
<%= link_to "", root_path, class: "navbar__brand navbar__mainLogo" %>が違うのでしょうか？

#application.html.erb

<!DOCTYPE html>
<html>
  <head>
    <title>Techgram</title>
    <%= csrf_meta_tags %>
    <%= csp_meta_tag %>

    <%= stylesheet_link_tag    'application', media: 'all', 'data-turbolinks-track': 'reload' %>
    <%= javascript_include_tag 'application', 'data-turbolinks-track': 'reload' %>
  </head>

  <body>
    <nav class="navbar navbar-expand-lg navbar-light">
      <div class="container">
        <%= link_to "", root_path, class: "navbar__brand navbar__mainLogo" %>
        <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
          <span class="navbar-toggler-icon"></span>
        </button>
        <div class="collapse navbar-collapse" id="navbarSupportedContent">
          <ul class="navbar-nav ml-md-auto align-items-center">
            <li>
              <%= link_to "投稿", "#", class: "btn btn-primary" %>
            </li>
            <li>
              <%= link_to "", "#", class: "nav-link commonNavIcon profile-icon" %>
            </li>
          </ul>
        </div>
      </div>
    </nav>

    <%= yield %>
  </body>
</html>

#application.scss

@import "bootstrap";
//= require bootstrap
@import "layouts/navbar";

#chrome
NameError in Pages#home
Showing C:/Users/sinta/techgram/app/views/layouts/application.html.erb where line #15 raised:

undefined local variable or method `root_path' for #<#Class:0x000000000841d748:0x000000000cd942f0>
Did you mean? font_path
#コマンドプロンプト
Started GET "/" for ::1 at 2019-06-01 17:32:04 +0900
Processing by PagesController#home as HTML
Rendering pages/home.html.erb within layouts/application
Rendered pages/home.html.erb within layouts/application (5.3ms)
Completed 500 Internal Server Error in 1809ms (ActiveRecord: 0.0ms)

ActionView::Template::Error (undefined local variable or method `root_path' for #<#Class:0x000000000846d810:0x0000000008484ee8>
Did you mean? font_path):
12: <body>
13: <nav class="navbar navbar-expand-lg navbar-light">
14: <div class="container">
15: <%= link_to "", root_path, class: "navbar__brand navbar__mainLogo" %>
16: <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
17: <span class="navbar-toggler-icon"></span>
18: </button>