Underspecified, as you appear to be using odd definitions of one or more terms. The straightforward interpretation of consecutive_differences (a, b, c, ... y, z) would be ((a - b), (b - c), ... (y - z)). Parsing the phrase "sum of consecutive differences of (2, 4, 5, 7)" as "sum (consecutive_differences (2, 4, 5, 6)))" and evaluating, one gets

sum (consecutive_differences(2, 4, 5, 7))
        = {definition of consecutive_differences}
sum((2 - 4), (4 - 5), (5 - 7))
        = {evaluate sub-expressions}
sum(-2, -1, -2)
        = {evaluate sum}
-5
[download]

but recognizing sum(a, b, c, ... z) as (a + b + c + ... + z), the above simplifies algebraically to

sum (consecutive_differences(2, 4, 5, 7))
        = {definition of consecutive differences}
sum((2 - 4), (4 - 5), (5 - 7))
        = {definition of sum}
((2 - 4) + (4 - 5) + (5 - 7))
        = {subtraction equals addition of negative}
(2 + -4 + 4 + -5 + 5 + -7)
        = {associativity and symmetry of addition}
(2 + (4 - 4) + (5 - 5) - 7)
        = {removal of zero terms}
(2 - 7)
        = {arithmetic}
-5
[download]

so that the "sum of consecutive differences" is the first minus the last.

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.