Question

Resolva as equações:
a)5x au quadrado -20=0
b)x au quadrado -81=0
c)x au quadrado +5x + 4=0

Answer 1

a)
5x² - 20 = 0
5x² = 20
x² = 20÷5
x² = 4
x = √4
x = 2

b)
x² -81 = 0
x² = 81
x = √81
x = 9

c)
x² + 5x + 4 = 0
(x+4)(x+1) = 0
x + 4 = 0
x = -4
x + 1 =0
x = -1

Answer 2

a) 5x²-20=0
5x²=20
x²=20/5
x²=4
x=√4=2
b) x²-81=0
x²=81
x=√81=9
c) x²+5x+4=0
∆= b²-4ac
∆=5²-4•1•4
∆=25-16=9
x=-b±√∆
---------------
2a
x=-5±√9
-------------
2•1
x=-5±3
------------
2
x'=-5+3=-2=-1
------ ----
2. 2 x"= -5-3= -8= -4 ------ ---- 2. 2