Answer:
[tex]\large \boxed{\sf \ \ y=(x-4)^2-1 \ \ }[/tex]
Step-by-step explanation:
Hello,
[tex]y = x^2-8x+15\\ \\\text{*** we need to complete the square ***} \\ \\y=(x-4)^2-4^2+15=(x-4)^2-16+15=(x-4)^2-1[/tex]
And then the vertex is (4, -1) and as a > 0 the vertex is a minimum.
Hope this helps.
Do not hesitate if you need further explanation.
Thank you