Question

como resolver?
a) x elevado a 2-12=0
b) 5x elevado a 2-3x=0
c) 7x elevado a 2-x=0
d) -15x elevado a 2-5x=0

obrigada!

Answer 1

$a) x^{2} -12=0\to\\\\ x^{2} =12\to\\\\ x= \sqrt{12} \to\\\\ x=3,46...$



$b)5 x^{2} -3x=0\\\\ 5x(x-3)=0\\\\ 5x=0\to x=-5\\\\x-3=0\to x=3\\\\\ S=(-5;3)$




$7 x^{2} -x\to 7x(x-1)=0 \\\\ 7x=0\to x=-7\\\\ x-1=0\to x=1\\\\ S=(-7;1)$




$d)-15 x^{2} -5x=0\\\\ -15x(x-5)=0\\\\ -15x=0\to x=15\\\\x-5=0\to x=5\\\\ S=(5,15)$

Answer 2

a)

x² - 12 = 0
x² = 12
x = √12
x = √4.√3

R.: x = + 2√3 ;  x = - 2√3
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b)
5x² - 3x = 0
x(5x - 3) = 0
x = 0

ou
5x - 3 = 0
5x = 3
x = 3/5

R.: x = 0 ou x = 3/5
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c)

7x² - x = 0
x(7x - 1) = 0
x = 0

ou

7x - 1 = 0
7x = 1
x = 1
      7

R.: x = 0 ou x = 1/7
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d)
- 15x² - 5x = 0
x(-15x - 5) = 0

x = 0

- 15x - 5 = 0
- 15x = 5 (:5)
- 3x = 1 (-1)
3x = - 1

x = - 1
        3

R.: x = 0 ou x = - 1/3