پاسخ : مشکل در apt-get update

سلام
من وقتی apt-get update رو میزنم آخرش بهم ارور های زیر رو نشون میده
چی باید بکنم که برطرف بشه؟
Reading package lists... Error!
W: The repository 'http://ppa.launchpad.net/chris-lea/node.js/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: The repository 'http://ppa.launchpad.net/upubuntu-com/tor64/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: There is no public key available for the following key IDs:
1397BC53640DB551
E: Failed to fetch http://ppa.launchpad.net/chris-lea/node.js/ubuntu/dists/xenial/main/binary-amd64/Packages  404  Not Found
E: Failed to fetch http://ppa.launchpad.net/chris-lea/node.js/ubuntu/dists/xenial/main/binary-i386/Packages  404  Not Found
E: Failed to fetch http://ppa.launchpad.net/upubuntu-com/tor64/ubuntu/dists/xenial/main/binary-amd64/Packages  404  Not Found
E: Failed to fetch http://ppa.launchpad.net/upubuntu-com/tor64/ubuntu/dists/xenial/main/binary-i386/Packages  404  Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
E: Unable to parse package file /var/lib/apt/lists/dl.google.com_linux_chrome_deb_dists_stable_main_binary-all_Packages (1)
W: You may want to run apt-get update to correct these problems
E: The package cache file is corrupted

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