19) Resolva as seguintes equações do 2º grau
a) x2 - 25 = 0
b) 2x - 32 = 0
c) 7x2 - 343 = 0
d) x2 - 81 = 0
) 2x2 - 50 = 0
e) x2 = 1
g) 7x? - 7 = 0
h) 5x2 - 15 = 0
1) 21 = 7x2
1) 5x2 + 20 = 0
k) 7x + 2 = 30
1) 2x2 - 90 = 8
m) 4x? - 27 = x
n) 8x2 = 60 - 7x
Respostas
Boa Noite !!!
Lembramos que quando um número passa ao outro lado inverte o sinal:
a) x² - 25 = 0
a) x = √25
a) x = 5
b) 2x² - 32 = 0
b) x² = 32/2
b) x² = 16
b) x = √16
b) x = 4
c) 7x² - 343
c) x² = 343/7
c) x² = 49
c) x = √49
c) x = 7
d) x² - 81
d) x = √81
d) x = 9
e) 2x² - 50 = 0
) x² = 50/2
) x² = 25
) x = √25
) x = 5
e) x² = 1
e) x = √1
e) x = 1
g) {7x} - 7 = 0
g) 7x = 7
g) x = 7/7
g) x = 1
h) 5x² - 15 = 0
h) 5x² = 15
h) x² = 15/5
h) x² = 3
h) x = √3
1) 21 = 7x²
1) 7x² = 21
1) x² = 21/7
1) x = √3 ou
1) x = 1,7320
1) 5x² + 20 = 0
1) x² = -20/5
1) x² = -4
1) x = ∉
k) 7x + 2 = 30
k) 7x = 30 - 2
k) 7x = 28
k) x = 28/7
k) x = 4
1) 2x² - 90 = 8
1) 2x² = 98
1) x² = 98/2
1) x² = 49
1) x = √49
1) x = 7
m) {4x} - 27 = x
m) 4x - x = 27
m) 3x = 27
m) x = 27/3
m) x = 9
n) 8 x 2 = 60 - 7x
n) 7x = 60 - 16
n) x = 44/7 ou
n) x = 6,2857
Resposta:
Explicação passo-a-passo:
a) x2 - 25 = 0 => x² = 25 => => x = ±5
b) 2x - 32 = 0 => 2x = 32 => x =
c) 7x2 - 343 = 0 => 7x² = 343 => => x = ±7
d) x2 - 81 = 0 => x² = 81=> => x = ±9
) 2x2 - 50 = 0 => 2x² = 50 => => x = ±5
e) x2 = 1 => => x = ±1
g) 7x? - 7 = 0 => 7x = 7 =>
h) 5x2 - 15 = 0 => 5x² = 15 =>x² = x = ±
1) 21 = 7x2 => -7x² = -21 => => x = ±
1) 5x2 + 20 = 0 => 5x² = -20 => x² = ∉
k) 7x + 2 = 30 => 7x = 30 - 2=> 7x = 28=> x =
1) 2x2 - 90 = 8 => 2x² = 8 + 90 => 2x² = 98 => => x = ±7
m) 4x? - 27 = x => 4x - x = 27 => 3x = 27 =>
n) 8x2 = 60 - 7x => 8x² + 7x -60 = 0 => Δ= b² -4ac=> Δ= (7)² -4(8)(-60)=>
Δ= 49 + 1920=> Δ= 1969
x = -b±√Δ/2a =>x = -7±√1969/2(8) =>