Question

7) conjunto solução da equação x²-3x-28=0 é

a)( ) [4.7]

b)( ) [-4,7]

c)( ) [-4.-7]

d)( ) [4,-7]​

Answer 1

Explicação passo-a-passo:

Resolvendo a equação usando Bhaskara:

$x^{2} -3x-28=0\\\\\Delta=(-3)^{2}-4.1.(-28)=9+112=121\\\\x'=\dfrac{-(-3)+\sqrt{121} }{2.1}=\dfrac{3+11}{2}\\\\x'=\dfrac{14}{2}\\\\\boxed{x'=7} \\\\x''=\dfrac{-(-3)-\sqrt{121} }{2.1}=\dfrac{3-11}{2}\\\\x''=\dfrac{-8}{2}\\\\\boxed{x''=-4}$

$\boxed{\boxed{S=\{-4,7\}}}$

Resposta B

Answer 2

x² - 3x - 28 = 0

∆ = b² - 4.a.c

∆ = (-3)² - 4.1.(-28)

∆ = 9 + 112

∆ = 121

$x = \frac{ - b ± \sqrt{∆} }{2 \times a}$

$x = \frac{ - ( - 8) ± \sqrt{121} }{2 \times 1}$

$x = \frac{8 ± 11}{2}$

$x' = \frac{3 + 11}{2} = \frac{14}{2} \\ x" = \frac{3 - 11}{2} = \frac{ - 8}{2}$

$x' = 7 \\ x" = - 4$

Letra B).