Moja propozycja. 
<div class="wrap">
<div class="slide"></div>
</div>
*, *::after, *::before {
-webkit-box-sizing: border-box;
-moz-box-sizing: border-box;
box-sizing: border-box;
}
:root {
--viewport_100_percent: 100vw;
}
html, body {
margin: 0;
padding: 0;
overflow-x: hidden;
}
.wrap {
width: var(--viewport_100_percent);
height: 400px;
overflow-x: hidden;
box-shadow: 2px 0px 5px 2px rgba(0,0,0,0.80);
}
.slide {
min-width: var(--viewport_100_percent);
min-height: 100%;
padding: 0;
background-image: url(https://source.unsplash.com/2000x401);
background-size: cover;
background-repeat: no-repeat;
}