Is this correct: first % in "Like" ignores indexes?

This is SQL 2014.

I'm doing a search query using Like %whatever%

Is this correct:
First %-sign will make any index useless, but one at the end will use the index.

I got it from here columns in Like
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CamilliaAsked:
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Jim HornSQL Server Data DudeCommented:
Yes that is correct.
WHERE whatever LIKE 'foo%' will use the index as the range is continuous.
WHERE whatever LIKE '%foo' will not.

I kid you not, that exact question was on one of my 70-761 practice exams.

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Raja Jegan RSQL Server DBA & Architect, EE Solution GuideCommented:
Yes, that's correct, % at the prefix will make the existing index useless for that query..
Scott PletcherSenior DBACommented:
A prefix of % does not make SQL "ignore" the index, it means that SQL can't do a seek on the index.  It could still scan the index to satisfy the query, and almost certainly will if that is the only condition in the WHERE clause.
CamilliaAuthor Commented:
Thanks, Scott
Jim HornSQL Server Data DudeCommented:
I stand correct.  Glad you said that, it might be on the exam.  Thanks Scott.
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