Completing this square here guys!

5x² + 5x + 11

Heres how i went through it;

5[x² + x] + 11

5[(x + 1/2)² - 1/4] + 11

5(x + 1/2)² - 5/4 + 11

5(x + 1/2)² + 39/4

but my book is giving me the answer of

5(x - 1/2)² + 39/4

and i really can't figure out why. probably something stupidly small, that i've missed, but i can't see it! :(

thanks for any help! :)

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