Question

Fatore os trinômios do 2° grau. a) x2 + 4x – 21 b) x2 – 9x + 20

Answer 1

Resposta:

a)

x² + 4x - 21

x²+4x+2²-2²-21

x²+4x+4 -25

(x+2)²-5²

=[(x+2)-5]*[(x+2)+5]

=(x-3)*(x+7)

b)

x² - 9x + 20

x²-9x+(9/2)²-(9/2)²+20

(x-9/2)²-81/4+20

(x-9/2)²-1/4

(x-9/2)²-(1/2)²

[(x-9/2) -1/2]*(x-9/2+1/2)

= (x-5)*(x-4)