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TS EAMCET · Maths · Quadratic Equation

Let the equations \(a x^2-7 x+c=0\) and \(a x^2+5 x-c=0\) have a common root and \(a c \neq 0\). If 3 is a root of \(a x^2-7 x+c=0\) other than the common root, then the common root of the given equations is

  1. A 3
  2. B \(\frac{1}{2}\)
  3. C 2
  4. D \(\frac{1}{3}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\frac{1}{2}\)

Step-by-step Solution

Detailed explanation

\[ \begin{aligned} & \text a x^2-7 x+c=0 \\ & a x^2+5 x-c=0 \end{aligned} \] Let common root be \(\alpha\) \[ \begin{aligned} & a \alpha^2-7 \alpha+c=0 \\ & a \alpha^2+5 \alpha-c=0 \\ & \frac{\alpha^2}{7 c-5 c}=\frac{\alpha}{a c+a c}=\frac{1}{5 a+7 a} \end{aligned} \]…