Which step can be used when solving x^2-6x-25=0?

Complete the square

since a=1 for ax²+bx²+c=0

we can do

take 1/2 of the linear coefient and square it

-6/2=-3, (-3) ²=9

add that to both sides

x²-3x+9-25=9

factor perfect square trinomial

(x-3) ²-25=9

add 25 to both sides

(x-3) ²=34

sqrt both sides, rmember to take positive and negative roots

x-3=+/-√34

add 3

x=3+/-√34

x=3+√34 or 3-√34