arme e Resolva as equaçoes :
a : 2x + 6 = x + 18
b : 5x - 3 = 2x + 9
c : 3 (2x - 3 ) + 2 (x + 1 ) = 3x + 18
d : 2x + 3 (2 - 5 ) = 4x + 9
e : 2 ( x + 1 ) - 3 ( 2x - 5 ) = 6x - 3
f : 3x - 5 = x - 2
g : 3x - 5 = 13
h : 3x + 5 = 2
i : x - (2x - 1 ) = 23
J : 2x - (x - 1) = 5 - (x - 3 )

2 : O valor numérico da expressão 2x² + 8 Para x igual - 3 e :
R =


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Respostas

2014-06-09T17:24:57-03:00
a) 2x+6=x+18 \\ 2x-x=18-6 \\ x=12 \\ \\ b)5x-3=2x+9 \\ 5x-2x=9+3 \\ 3x=12 \\  \\ x =  \frac{12}{3} \\ \\ x=4

c)3.(2x-3)+2.(x+1)=3x+18\\6x-9+2x+2=3x+18\\6x+2x-3x=18+9-2\\5x=25\\\\x=\frac{25}{5} \\\\ x=5\\\\d)2x+3.(2-5)=4x+9\\2x+3.(-3)=4x+9\\2x-9=4x+9\\2x-4x=9+9\\-2x=18\\\\x=\frac{18}{-2}\\\\x=-9

e)2.(x+1)-3.(2x-5)=6x-3\\2x+2-6x+15=6x-3\\2x-6x-6x=-3-2-15\\-10x=-20; (multiplica-1)\\10x=20\\\\x=\frac{20}{10}\\\\x=2

f)3x-5=x-2\\3x-x=-2+5\\2x=3\\\\x=\frac{3}{2}; ou\\\\x=1,5

g)3x-5=13\\3x=13+5\\3x=18\\\\x= \frac{18}{3}\\\\ x=6

h)3x+5=2\\3x=2-5\\3x=-3\\\\x= \frac{-3}{3}\\\\x=-1

i)x-(2x-1)=23\\x-2x+1=23\\-x=23-1\\-x=22; (multiplica-1)\\x=-22

j)2x-(x-1)=5-(x-3)\\2x-x+1=5-x+3\\2x-x+x=5+3-1\\2x=7\\\\x= \frac{7}{2} ; ou\\\\ x= 3,5

2)2x^2+8=-3\\2x^2+8+3\\2x^2+11=0

Δ = 0^2-4.2.11
Δ = 0-88
Δ = -88

Não há raíz para delta negativo.

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