Respostas

2014-05-13T11:14:08-03:00
A)
(4+x²)/8=5
4+x²= 40
X² = 36
X= √ 36
X = 6

B)
(X-4)² = 9
(X-4)(X-4)=9
X²-8x+16=9
X²-8x+7=0

a=1 b=-8 c=7

D=b²-4.a.c
D=-8²-4.1.7
D=64-28
D=36



x=(-b+-√D)/2.a
X=(-(-8)+-√36)/2
x'=7
x''=1


C)
(X-4).(x+4)=2.(7x-8)
X²-16=14x-16
X² -14x=0

D=-14²-4.1.0
D= 196


X=(14+- √196)/2
X'= 0
X"= 14