JEE Mains · Maths · STD 11 - 4.2 Quadratic equations and inequations
If the equations \(x^2 + bx - 1 = 0\) and \(x^2 + x + b= 0\) have a common root different from \(-1,\) then \(\left| b \right|\) is equal to
- A \(2\)
- B \(3\)
- C \(\sqrt 3\)
- D \(\sqrt 2\)
Answer & Solution
Correct Answer
(C) \(\sqrt 3\)
Step-by-step Solution
Detailed explanation
\(x^{2}+b x-1=0\) common root \(x^{2}+x+b=0\) \(x=\frac{b+1}{b-1}\) Put \(x=\frac{b+1}{b-1}\) in equation \(..........(2)\) \(\left(\frac{b+1}{b-1}\right)^{2}+\left(\frac{b+1}{b-1}\right)+b=0\) \((b+1)^{2}+(b+1)(b-1)+b(b-1)^{2}=0\)…
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