Question

resolva as equações de 2° grau. A)2x²+2x-84=0 B)-3x²+9x=0​

Answer 1

a) a= 2, b= 2, c= -84

Δ= b² - 4 × a × c

Δ= 2² - 4 × 2 × (-84)

Δ= 4 + 672

Δ= 676

X= – b ± √Δ ÷

        2 × a

X= –2 ± √676 ÷

        2 × 2

X= – 2 ± 26 ÷

        4

x'= 24 ÷ 4 = 6

x"= -28 ÷ 4 = -7

b) a= -3, b= 9, c=0

Δ= b² - 4 × a × c

Δ= 9² - 4 × (-3) × 0

Δ= 81

X= – b ± √Δ ÷

        2 × a

X= -9 ± √81 ÷

       2 × (-3)

X= – 9 ± 9 ÷

        -6

x'= -9 + 9= 0

x"=-18 ÷ -6= 3