Question

ache as raizes das equações

a) x² - x - 20 = 0

b) x² - 3 x - 4 = 0

c) x² - 8 x + 7 = 0​

Answer 1

Resposta:

A)

 x1=5

x2=-4

B)

x1=4

x2=-1

C)

x1=7

x2=1

Explicação passo-a-passo:

Usarei a formula de bhaskara em todas as tres equacoes:

formula: -b +- raiz( b^2 -4.a.c) /2.a

A) a=1 , b=-1 , c=-20

1 +- raiz( (-1)^2 -4.1.(-20)) / 2.1 => 1+- raiz( 1+80) /2

=> 1+-raiz(81) /2 =>( 1+-9) /2

x1 = (1+9)/2 => x1=5

x2 = (1-9)/2 => x2=-4

B) a=1 , b=-3 , c=-4

3+- raiz( (-3)^2 -4.1.(-4)) /2.1 =>  3+- raiz(9+16) /2

=> 3+- raiz(25)/2 => (3+-5) /2

x1= (3+5)/2 => 8/2 => x1=4

x2= (3-5)/2 => -2/2 => x2=-1

C) a=1 , b=-8 , c=7

8+- raiz((-8)^2 -4.1.7) /2.1 => 8+- raiz(64-28) /2

=> 8+- raiz(36) /2 => (8+-6) /2

x1= (8+6)/2=> 14/2 => x1=7

x2=( 8-6)/2 => 2/2 => x2=1