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Question
Solve the following quadratic equation:
x2 + 4x – 8 = 0
Give your Solution correct to one decimal place.
(Use mathematical tables if necessary.)
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Solution
Given: x2 + 4x – 8 = 0
Here a = 1, b = 4, c = – 8
D = b2 – 4ac
= (4)2 – 4 × 1 × (– 8)
= 16 + 32
= 48 > 0
∴ Roots are real.
So, x = `(-b ± sqrt(D))/(2a)`
x = `(-4 ± sqrt(48))/(2 xx 1)`
= `(-4 ± 4sqrt(3))/2`
= `-2 ± 2sqrt(3)`
x = `-2 ± (2 xx 1.73)` ...`{∵ sqrt(3) = 1.73}`
= – 2 ± 3.46
`\implies` x = 1.46, – 5.46
or x = 1.5, – 5.5 ...(Correct to one decimal place)
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