Verified answer

X^2 - 4X - 5 = 7

X^2 - 4X - 5 - 7 = 0

X^2 - 4X - 12 = 0

a = 1

b = -4

c = -12

Δ = b^2 - 4ac

Δ = ( - 4 )^2 - 4 • 1 • ( - 12 )

Δ = 16 + 48

Δ = 64

X = -b ± √Δ /2a

X = 4 ± √64 /2 • 1

X = 4 ± 8 /2

X' = 4 + 8 /2 = 12/2 = 6

X'' = 4 - 8 /2 = -4/2 = -2

x^2 -4x-5=7

x² - 4x - 5 = 7

x² - 4x - 12 = 0

x = (4 +/- ²v16 + 48)/2

x = (4 +/- ²v64)/2

x = (4 +/- 8)/2

x = 2 +/- 4

x' = 2 + 4

x' = 6

x'' = 2 - 4

x'' = -2

x² - 4x - 12 = 0

d² = 16 + 48 = 64

d = 8

x1 = (4 + 8)/2 = 6

x2 = (4 - 8)/2 = -2

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