You need to complete the square.
(b-/2(a))^2
(-26/2(1))^2 = 169
add to both sides
x^2+26x+169 = 456 + 169
now add everything together and cut b in half and place the exponent outside..
(x+13)^2 = 625
now find the a sqaure root of 625 and drop the parenthesis on the other side ..
x+ 13 = +/- 25
this means plus or minus 25...minus 13 from each side...
x= -13 +/- 25
now solve both equations to get the min and max x...
-13 -25 = -38
-13 + 25 = 12
x= -38 and x= 12
