需要帮助理解证明题答案 need help understanding proof

[dusk breach]

1. Wait patiently for a helper to come along.
2. Once someone helps you, say thank you and close the thread with:

+close

3. Feel free to nominate the person for helper of the week in #helper-nominations
4. Do not ping the mods, unless someone is breaking the rules.
5. If you're happy with the help you got here, and the server overall, you can contribute financially as well:

[lilac badge]

i only need help for (2)

btw

the first two pictures is the problem, and the last one is the answer

nvm i think i understand now

bruh

[surreal saffron]

if you dont neede help anymore, type +close

[lilac badge]

+close