Multiple choice

Two persons A and B solved a quadratic equation of the form x2 + bx + c = 0. A made a mistake in noting down the coefficient of x and obtained the roots as 18 and 2, where as B obtained the roots as – 9 and – 3 by misreading the constant term, find the correct roots of the equation.

  1. – 6 , – 3

  2. – 6 , 6

  3. – 6 , – 5

  4. – 6 , – 6
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D Correct answer
Explanation

A misread b, so c is correct: roots 18, 2 => c = 18*2 = 36. B misread c, so b is correct: roots -9, -3 => -b = -9 + -3 = -12 => b = 12. Equation is x^2 + 12x + 36 = 0. Roots are (x+6)^2 = 0 => x = -6, -6.

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