1)x^2-6x=5=0 2)x^2 =4x-5=0 3)(4-x)(4=x)=x^2-2

x^2-6x+5=0

D=4b^2-4ac=-6^2-4*1*5=36-20=16

VD = V16 = 4

        - b+ - VD

x =

             2a

x1 = (6+4)/2 = 10/2=5

x2 = (6-4)/2 = 2/2=1

OTBET: x=1 i x=5

x^2 +4x-5=0

D = 4^2-4*1*-5 = 16- (-20) = 16+20 = 36

VD = V36 = 6

x1 = (-4+6)/2 = 2/2 = 1

x2 = (-4-6)/2 = -10/2 = -5

OTBET:  x=-5 i x=1

(4-x)(4+x)=x^2-2

16+4x-4x-x^2 = x^2-2

16+4x-4x-x^2- x^2+2 =0

-2x^2+18=0   / :(-2)

x^2 = 9

 x= + - 3

кажется,так :)