Question

Achar as raizes das equações precisar fazer o cálculo:

a)X²-x-20=0?

b)X²-3x-4=0?

c)X²-8×+7=0?

Answer 1

Resposta:

a)s={-4,5}

b) s={4, -1}

c) s={ 7, 1}

Explicação passo-a-passo:

a) a=1

b=-1

c=-20

Δ= b² - 4ac

Δ= (-1)² - 4.1.(-20)

Δ=1+80

Δ= 81

$\frac{-b+/-\sqrt{delta} }{2a}$                   Δ=delta

$\frac{-(-1)+/-\sqrt{81} }{2.1}$

$\frac{1+/-9}{2}$$\left \{ {{x'=\frac{1+9}{2}=\frac{10}{2}=5 } \atop {x"=\frac{1-9}{2}=\frac{-8}{2}=-4 }} \right.$

b)a=1

b=-3

c=-4

Δ= b²-4ac

Δ=(-3)²-4.1.(-4)

Δ= 9+16

Δ=25

$\frac{-b+-\sqrt{delta} }{2a}$

$\frac{-(-3)+/-\sqrt{25} }{2}$

$\frac{3+/-5}{2}$$\left \{ {{x'=\frac{3+5}{2} }=\frac{8}{2}=4 \atop {x"=\frac{3-5}{2}=\frac{-2}{2} }}$

c)a=1

b=-8

c=7

Δ= b²-4ac

Δ=(-8)²-4.1.7

Δ=64-28

Δ=36

$\frac{-b+/-\sqrt{delta} }{2a}$

$\frac{-(-8)+/-\sqrt{36} }{2.1}$

$\frac{8+/-6}{2}$=$\left \{ {{x'=\frac{8+6}{2}=\frac{14}{2}=7 } \atop {x"=\frac{8-6}{2}=\frac{2}{2}=1 }} \right.$