y = (x^2 + 26x) +160 complete the square
y = (x^2 + 26x ) + 160
Split our the constant and use the (b/2)^2
y = (x^2 + 26x + (26/2)^2 ) + 160 - (26/2)^2
since I am adding the new value I must subtract it from the end to keep the balance
y = (x^2 + 26x + 169) + 160 - 169
Now factor parenthesis and combine like terms
y = (x+13)^2 -9 its in the vertex form