4c^2-8c-1=0 complete the square round to nearest hundredth

Move constant to other side

add 1

4c^2-8c=1

divide by 4 to make leading coeficient 1

c^2-2c=1/4

take 1/2 of linear coeficient and square it

-2/2=-1, (-1) ^2=1

add that to both sides

c^2-2c+1=1/4+1

factor perfect squaer and add

(c-1) ^2=5/4

square root both sides

c-1 = + / - (√5) / 2

add 1

c=1 + / - (√5) / 2

c=2.12 or - 0.12