Answer:
The equation is : x-2y+2=0.
bearing in mind that an explicit form is simply the sequence written as a function of some variables, so we simply simplify and add like-terms.

If I am reading the question correctly it would come out to -6x+42 First do all the addition and squaring, then factor in that negative. You come out to -2x^3 +2x^3-4x-2x+25+5+9+3. The x^3's cancel, the -x's add to -6x, then all that other adds to 42.
The median is the middle value, so put them all in numerical order, (1,2,4,6,7, ect.), and find the middle. If there is two numbers in the middle find the number exactly between them.
Hope this helps!