help

I think the answer is wrong

The answer Geno gave is almost right; he just made a small error in the final step:

Geno's answer:

   3x² + 12x + 4

=  3(x² + 4x) + 4

=  3(x² + 4x + 4) + 4 - 12

=  3(x + 2)² - 12     This last line should be 3(x + 2)² - 8   (as 4 - 12 = -8)

so a = 3, h = -2, and k = -8