update chapter-2
add img
Update chapter-2.md
add images
Update chapter-2.md
Update chapter-2.md
add images
Update chapter-2.md
add images
Update chapter-2.md
add images
Update chapter-2.md
add code
fix typo
Update chapter-2.md
add images
Update chapter-2.md
add images and code
Update chapter-2.md
add images