Question

20 pts!!!! As raizes da equação 5(x+2)(x-1/5)=0 são:

a) 2e 5
B) 2 e -1/5
c)10 e 25
d) -2 e 1/5
e) -2 e 1/5

Answer 1

(5x + 10)(x - 1/5) = 0
5x^2 - x + 10x - 2 = 0
5x^2 + 9x - 2 = 0

delta = 9^2 - 4 . 5 . (-2) = 81 + 40 = 121

x = -9 +-√121/2 . 5 = -9 +- 11/10 
x' = -9 + 11/10 = 2/10 = 1/5
x" = -9 -11/10 = -20/10 = -2