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Question
Solve : x2 – 11x – 12 =0; when x ∈ N
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Solution
x2 – 11x – 12 =0
`=> x^2 - 12x + x - 12 = 0`
=> x(x - 12) + 1(x - 12) = 0
=> (x - 12)(x + 1) = 0
then x = 12 and x = -1
Since `x in N` then x = 12
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