Given six digits 1, 2, 3, 4, 5 and 6. a) Determine the number of four-digit numbers that can be formed using the digits given

if no repetition is allowed.

b) How many four-digit numbers greater than 4,000 can be formed using the digits given
without repetition?​

Given: ae ≅ ce ; de ≅ be prove: abcd is a parallelogram. we have that ab || dc. by a similar argument used to prove that △aeb ≅ △ced, we can show that △ ≅ △ceb by. so, ∠cad ≅ ∠ by cpctc. therefore, ad || bc by the converse of the theorem. since both pair of opposite sides are parallel, quadrilateral abcd is a parallelogram.