if x is a sum of all even integers on the interval 13 . . . 63 and y is their number , what is the gcd ( x , y ) ?
x = 14 + 16 + . . . + 62 = ( largest + smallest ) / 2 * ( # of terms ) = ( 14 + 62 ) / 2 * 25 = 38 * 25 . gcd of 25 and 39 * 25 is 25 . answer : d .
multiply(add(subtract(13, const_10), const_2), add(subtract(13, const_10), const_2))