Write p(x) = 21 + 24x + 6x2 in vertex form. p(x) = (x +__ )2 –

Vertex form is basically, just complete the square on the right side
group x terms together

factor out linear coefient (number in front of the higest power x, in this case x^2)

take 1/2 of the linear coefient and square it (4 is linear coefient so take 1/2 of it and square it (4/2=4, 4^2=4)), add positive and negative of it inside the parenthaees (so it equals 0)

factor perfect square trinomial
distribute (don't distribute or expand the squared term)

Your maths is very weak try yourself this would improve your skills don't depend on others