Question

Resolva as equações

a) x² - 20 = 0
b) x² -3x - 4=0
c) x² - 8x +7 = 0
d) 3x² - 7x + 4 = 0​

Answer 1

Resposta:

A

$x^2 - 20 = 0\\x^2= 20\\x = \sqrt{20} \\x = 4,48$

B

$x^2 - 3x - 4=0\\\\a=1\\b= -3\\c= -4\\\\x^2 -3x - 4=0\\Δ = b^2 -4ac\\Δ= (-3)^2 - 4.1.(-4)\\Δ= 9 + 16\\Δ= 115$   neste caso o Î= Δentão onde for copiar coloque o Δ que é delta

C

$x^2 - 8x +7 = 0\\a=1\\b=-8\\c=7\\\\Δ= b^2 -4ac\\Δ= -(-8)^2 -4.1.7\\Δ= 64 - 28\\Δ= 36\\\\x = \frac{-b +/- \sqrt{Δ} }{2a}\\x=\frac{8 + 6}{2}\\x= \frac{14}{2}\\x= 7\\\\x= \frac{8 - 6}{2}\\x= \frac{2}{2}\\x=2$

d

$3x^2 - 7x + 4 = 0​\\a=3\\b=-7\\c=4\\\\Δ= b^2 - 4ac\\Δ= (-7)^2-4.3.4\\Δ= 49 - 48\\Δ= 1 \\x = \frac{-b+/- \sqrt{Δ} }{2a}\\x = \frac{-(-7)+ 1 }{2.3}\\x = \frac{8}{6} \\x = ≅ 2,3 \\\\x= \frac{-(-7) - 1}{2.3}\\x= \frac{6}{6}\\x= 1$

Explicação passo a passo: