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  • Answer please! - Complex numbers and quadratic equations - JEE Main-9

If f (x) is a quadratic expression such that f (1)+f (2)=0 , and −1 is a root of f (x)=0, then the other root of f (x)=0 is :

  • Option 1)

    -\frac{5}{8}

  • Option 2)

    -\frac{8}{5}

  • Option 3)

    \frac{5}{8}

  • Option 4)

    \frac{8}{5}

 

Answers (1)

As we learned

 

One root = \beta =-1  ,  other = \alpha

f\left ( x \right )=x^{2}+\left ( 1-\alpha \right )x-\alpha

f\left ( 1 \right )=2-2\alpha

f\left ( 2 \right )=6-3\alpha

f\left ( 1 \right )+f\left ( 2 \right )=2-2\alpha +6-3\alpha =0

\Rightarrow \: \alpha =\frac{8}{5}


Option 1)

-\frac{5}{8}

Option 2)

-\frac{8}{5}

Option 3)

\frac{5}{8}

Option 4)

\frac{8}{5}

Posted by

Vakul

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