Not sure I understand your question but I'll give it a try.
AB = 4,
2 AB = 2 * 4 = 8
CD = 7
EF = 1
2AB - 1CD = EF
8 - 7 = 1
You are given two segments, with AB = 4 and with CD = 7. Explain how you could use only the congruent-segments construction to construct with EF = 1.
2 answers
2x+63= 4x+2