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.... :)