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The value of k for which the equation 2x2 – (k-1) x+8=0 will have real and equal roots are :(a) 9 and -7(b) only 9(C) only - 7 (d) -9 and - 7 |
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Answer» Answer: option a is correct, i.e. 9 and -7 Step-by-step explanation: SINCE roots are equal and real. so, D=0 D=b²-4ac so, b²-4ac=0 (-(k-1))²-4×2×8=0 k²-2k+1-64=0 k²-2k-63=0 k²-9k+7k-63=0 k(k-9)+7(k-9)=0 (k-9)(k+7)=0 so, k=9, -7 |
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