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Question
Solve the following quadratic equation using formula method only
x2 - 4x - 1 = 0
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Solution
x2 - 4x - 1 = 0
a =1 ; b = -4 ; c =-1
D = b2 - 4ac
= (-4)2 - 4(1)(-1)
= 16 + 4
= 20
x =`(- "b" ± sqrt ("b"^2 - 4 "ac"))/(2a)`
x = `(4 +- sqrt 20)/2`
x = `(4 +- 2sqrt 5)/2`
x = 2 + `sqrt 5` , x = 2 - `sqrt 5`
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