Tolong bantu jawab!

X² – x – 20 = 0
(x-5) (x+4) = 0
x1 = 5
x2 = -4

persamaan baru
x1' = x1-3 = 5-3 =2
x2' = x2-3 = -4-3 = -7

persamaan baru
(x-2)(x+7)=0
x²-5x-14 = 0