√27-√75+√243 = √(9*3) - √(25*3) + √(81*3) = 3√3 - 5√3 + 9√3 = 7√3.
(x-4)(x-b)=x^2-4x-bx+4b
-4-b=1
b=-5
a=-20
(x-4)(x+5)=x^2-4x+5x-20=x^2+x-20
Відповідь буде така x<-20
(2/(n+1)! - 3/n!) : (5/n!- 4n/(n+1)!)
1) 2/ (n+1)! -3/ n!= 2/(n+1)! - 3(n+1)/(n+1)! = (2-3n-3) / (n+1)!
2) 5/n! - 4n/(n+1)! = (5(n+1) -4n) / (n+1)! = (n+5)/ (n+1)!
3) (-3n-1)/ (n+1)! : ((n+5)/(n+1)!)= (-3n-1)(n+1)! / (n+1)!(5+n) =
= (-3n-1) / (5+n)
ответ при n = 2