Respostas

  • Usuário do Brainly
2013-10-08T21:08:06-03:00
J)
- 4x'' + 28x = 0
4x(-x + 7) = 0
4x = 0
x = 0/4
x = 0

- x + 7 = 0
- x = - 7 .(-1)
x = 7

S = { 0, 7 }

k)
x'' - 20 = 0
x'' = 20
mmc de 20
20/2
10/2
5/5
1

(2'' . 5)

x = +_  \sqrt{20}
x = +_ 2 \sqrt{5}

S = ( - 2 \sqrt{5} , 2 \sqrt{5}  )

l)
- 15x'' - 5x = 0 .(-1)
15x'' + 5x = 0
5x.(3x + 1) = 0
5x = 0
x = 0/5
x = 0

3x + 1 = 0
3x = - 1
x = - 1/3

S = { 0, -1/3 }

2 5 2