Mathematics
Find the value of k for which x = 3 is a solution of the quadratic equation (k + 2)x2 - kx + 6 = 0.
Thus, find the other root of the equation.
Quadratic Equations
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Answer
Substituting, x = 3 in (k + 2)x2 - kx + 6 = 0 we get,
⇒ (k + 2)(3)2 - 3k + 6 = 0
⇒ (k + 2)(9) - 3k + 6 = 0
⇒ 9k + 18 - 3k + 6 = 0
⇒ 6k + 24 = 0
⇒ 6k = -24
⇒ k =
⇒ k = -4.
Substitute the value of k = -4 in (k + 2)x2 - kx + 6 = 0 we get,
⇒ (-4 + 2)(x)2 - (-4)x + 6 = 0
⇒ (-2)(x)2 - (-4)x + 6 = 0
⇒ -2x2 + 4x + 6 = 0
⇒ -2x2 - 2x + 6x + 6 = 0
⇒ -2x(x + 1) + 6(x + 1) = 0
⇒ (x + 1)(-2x + 6) = 0
⇒ (x + 1) = 0 or (-2x + 6) = 0 [Using Zero-product rule]
⇒ x = -1 or -2x = -6
⇒ x = -1 or x =
⇒ x = -1 or x = 3.
Hence, the value of k = -4 and the other root is -1.
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