Question

Calcule os zeros da função do 2° grau incompletas

a) f(x) = 1/3x² - 6

b) f(x) = -2/5x² + 3

c) f(x) = -x² + 4/3

d) f(x) = -3/2 ײ + 2/5

Answer 1

Oie, tudo bom?

a)

f(x) = 1/3 x² - 6

0 = 1/3 x² - 6

- 1/3 x² = - 6 . (- 3)

x² = 18

x = ± √18 √(3² . 2) = √(3²)√2

x = ± 3√2

S = {- 3√2 , 3√2}

b)

f(x) = - 2/5 x² + 3

0 = - 2/5 x² + 3

2/5 x² = 3 . (5/2)

x² = 15/2

x = ± √(15/2) √15/√2 = √15/√2 . √2/√2

x = ± (√30)/2

S = {- (√30)/2 , (√30)/2}

c)

f(x) = - x² + 4/3

0 = - x² + 4/3

x² = 4/3

x = ± √(4/3) 2/√3 = 2/√3 . √3/√3

x = ± (2√3)/3

S = {- (2√3)/3 , (2√3)/3}

d)

f(x) = - 3/2 x² + 2/5

0 = - 3/2 x² + 2/5

3/2 x² = 2/5 . (2/3)

x² = 4/15

x = ± √(4/15) 2/√15 = 2/√15 . √15/√15

x = ± (2√15)/15

S = {- (2√15)/15 , (2√15)/15}

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