Question

resolva as equações do 2 grau:
(a) 4x²-64=0
(b) 7x²-21=0
(c) 5.(x²-1)=4..(x²+1)
(d) x²-7x=0
(e) 3x²-4x=0
(f) (x-5).(x-6) = 30

Answer 1

(a) 4x² - 64 = 0
4x² = 0 + 64
4x² = 64
x² = 64/4
x² = 16
x = √16
x= 4

(b) 7x² - 21 = 0
7x² = 0 + 21
7x² = 21
x² = 21/7
x = 3
x = √3
x = 1,73...

(c) 5.(x²-1) = 4.(x²+1)
5x² - 5 = 4x² + 4
5x² - 4x² = 4 + 5
x² = 9
x = √9
x = 3

(d) x² - 7x = 0
x.(x-7) = 0
x' = 0
x"-7 = 0
x"=7
S = {0 / 7}

(e) 3x² - 4x = 0
x.(3x-4) = 0
x' = 0
3x"-4 = 0
3x" = 0 + 4
3x" = 4
x" = 4/3
x" = 1,33...
S = {0 / 1,33...}

(f) (x-5).(x-6) = 30
x² - 6x - 5x + 30 = 30
x² - 11x = 30 - 30
x² - 11x = 0
x.(x-11)  = 0
x' = 0
x"-11 = 0
x" = 0 + 11
x" = 11
S = {0 / 11}