Question

6°Calcule as raizes da equaçao:a)5x²-20=0b) √2/3x²=0c)x²+x/5=0d)7x²-21=0e)2x²+5x=0f)-x²+4=0

Answer 1

a)5x²-20=0 ==> 5x²=20 ==> x²=4 ==> x=+/- 2
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b) √2/3x² = 0 ==> x² = 0/√2/3 ==> x²=0 ==> x = 0
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c)x²+x/5=0 ==> 5x² - x =0 ==> x(5x - 1) = 0

x1 = 0  ;  

5x2 - 1 = 0 ==> 5x2 = 1 ==> x2 = 1/5
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d)7x²-21=0 ==> 7x² = 21 ==> x² = 3 ==> x = +/-√3
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e)2x²+5x=0

2x² + 5x =0 ==> x(2x + 5) = 0

x1 = 0  ;   

2x2 + 5 = 0 ==> 2x2 = - 5 ==> x2 = - 5/2
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f) - x²+4=0 ==> - x²+4=0 ==> - x² = - 4(-1) ==> x² = +4 ==> x = +/- 2