3. Which of the following is a square of a binomial?


[tex]a. \: 76x {}^{2} \: 16x \: + 4 \\ b.x {}^{2} - 6x - 9 \\ c. \: x {}^{2} + 5x + 9 \\ d. x{}^{2} + 6x - 9[/tex]
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