Respostas

2013-07-04T19:18:47-03:00
-20x^2-5x=0

-5x(4x+1)=0

-5x=0 x =0   4x+1=0  ... x=-1/4

confere?

2013-07-04T19:24:30-03:00
-20x²-5x=0
a= -20
b= -5
c=0

Delta= b²- 4*a*c
Delta= -5² - 4* (-20) *0
Delta= 25 -0
Delta= 25

x¹= -b+VDelta/2*a
x¹= - (-5) + V25/2* (-20)
x¹= 5+5/-40
x¹=10/-40 (simplifica por 10)
x¹= -1/4

x²= -b-VDelta/2*a
x²= -(-5)-V25/ 2* (-20)
x²= 5 -5 / -40
x²= 0/-40
x²= 0