Question

Write the quadratic function in vertex form.

y = x2 + 18x + 71

Answer 1

it is going to look like \(y=(x+9)^2+k\) for some \(k\)
to find \(k\) replace \(x\) by \(-9\) in the original expression and see what you get
because \(y=(-9+9)^2+k=0+k=k\)