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Question
If one of the roots of quadratic equation x2 + kx + 54 = 0 is – 6, then complete the following activity to find the value of ‘k’.
Activity: One of the roots of the quadratic equation x2 + kx + 54 = 0 is – 6.
Therefore let’s take x = ______
(– 6)2 + k(– 6) + 54 = 0
(______) – 6k + 54 = 0
– 6k + ______ = 0
k = ______
Solution
One of the roots of the quadratic equation x2 + kx + 54 = 0 is – 6.
Therefore let’s take x = − 6
∴ (– 6)2 + k(– 6) + 54 = 0
∴ 36 – 6k + 54 = 0
∴ – 6k + 90 = 0
∴ 6k = 90
∴ k = `90/6`
∴ k = 15
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