Question

Помогите пожалуйста умоляю​

Answer 1

1) (5х +1)(5х-1) - 20х(х-1) + 4 = 0

25х^2 - 1 - 20х^2 + 20х + 4 = 0

5х^2 + 20х + 3 = 0

D = 20^2 - 4•5•3 = 400 - 60 = 240

√D = √240 = 4√15

х1 = (-20 + 4√15)/(2•5) = (-20 + 4√15)/10

х2 = (-20 - 4√15)/(2•5) = (-20 - 4√15)/10

2) 15 • х1 • х2 =

= 15 • (-20 + 4√15)/10)((-20 - 4√15)/10 =

= 15• (-(20 - 4√15)/10)) • (-(20 + 4√15)/10)) =

= 15 • ((20^2 - (4√15)^2) /100

= 15 • (400 - 16•15) / 100=

= 15 • (400 - 240) / 100 =

= 15 • 60 / 100 = 900/100 = 9

Ответ: 9.