Question

resolva estas questoes

a)4x²-4x-35=0
b)2x²-x-1=0
c)9x²-18x-7=0

Answer 1

Resposta:

Explicação passo-a-passo:

a) x²-4x-35=0

a = 4

b = -4

c = -35

Δ = b² - 4.a.c

Δ = (-4)² - 4.4.(-35)

Δ  = 16 + 560

Δ = 576

-b +- √Δ / 2.a

-(-4) +- √576 / 2.4

4 +- 24 / 8

x' = 4+24/8 = 28:4/8:4 = 7/2

x'' = 4-24/8 = -20:4/8:4 = -5/2

s = {x' = 7/2; x" = -5/2}

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b)

2x²-x-1=0

2x²+x-1=0

a=2  b= 1 c=-1

Δ=b²-4.a.c

Δ= 1²-4.2.(-1)

Δ= 1+8

Δ=9

x=-b+/-√Δ/2.a

x=-1+/-√9/2.2

x=-1+/-3/4

x'= -1+3/4

x'= +2/4

x'=0,5 ou 1/2.

x"= -1-3/4

x"= -4/4

x"= -1

s = {x' = 2/4 e x'' = -1}

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c)

9x²-18x-7=0

9x²-18x-7=0

a=9

b=-18

c=-7

Δ=b² -4ac

Δ=(-18)²-4*9*(-7)

Δ=324+252

Δ=576

x=-b+-√Δ / 2a

x=-(-18)+-√576 / 2*9

x=18+-24 /18

x'=18+24 / 18

x'=42/18 ⇒7/3

x''= 18-24/18

x''=-6/18⇒1/3

s = {x'=7/3 e x''=1/3}