the roots of equation 9x^2-2(k+1)x+ 49=0 are equal , then k is?
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Answer:
k = -22 or 20
Step-by-step explanation:
Since roots of equation are equal,
b² - 4ac = 0
[-2(k+1)]² - 4 * 9 * 49 = 0
=> 4(k²+2k+1) - 1764 = 0
=> 4k² + 8k + 4 - 1764 = 0
=> 4k² + 8k - 1760 = 0
=> 4 (k²+ 2k - 440) = 0
=> k²+ 2k - 440 = 0
=> k² + 22k - 20k - 440 = 0
=> (k+22)(k-20) = 0
=> k = -22 or 20
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