Verified answer

A) (-x^2+1). (x^2-3x+2)=0

(1-x²). (x²-3x+2) = 0

(1+x).(1-x). (x-1).(x-2) = 0

x'=-1..x''=1...x'''=1..x''''=2

B) (2x+1).(-4x^2-1)=0

2x=-1.......4x²=-1

x' =-1/2....x''= { }

C) (x-1).(x-2)=(x-1).(2x+3)

x²-3x+2 = 2x²+x-3

x²+4x-5=0

-b/c = -4/-5 = 1-5/1.-5 => S:{1, -5}

D) (x+5)^2=(2x-2)^2

x²+10x+25 =4x²-8x+4

4x²-x² -8x-10x +4-25 = 0

3x²-18x-21=0.....=> (:3)

x² -6x -7 = 0

-b/c = -6/-7 = 1-7/1.-7 => S:{1, -7}

E) x^3+10x^2+21x=0

x(x²+10x+21) = 0.........=> x'=0

(x²+10x+21) = 0

-b/c = -10/21 = -7-3/-7.-3 => S:{-7, -3, 0}