ubuntu on hyper-v

hi guys
a couple a days ago i installed ubuntu on the virtual machine (hyper-v) and ha some resolution problems.
i found a nice guide how to fix it https://blogs.msdn.microsoft.com/vir...-a-hyper-v-vm/ .
i inserted the changes to the grub line and after i performed : sudo update-grub the output was:

/usr/sbin/grub-mkconfig: 35: /etc/default/grub: Syntax error: EOF in backquote substitution

what is it and what can i do from here?

tnx a lot