Hi there! The correct answer is the third.
[tex]f(x) = 3 {x}^{2} + 12x + 11 \\ f(x) = 3( {x}^{2} + 4x) + 11 \\ f(x) = 3((x + 2) {}^{2} - {2}^{2} ) + 11 \\ f(x) = 3((x + 2) {}^{2} - 4) + 11 \\ f(x) = (x + 2) {}^{2} - 12 + 11 \\ f(x) = (x + 2) {}^{2} - 1[/tex]
~Hope this helps you!
