10th Class Mathematics Quadratic Equations Question Bank Quadratic Equation

  • question_answer
    If a 2nd degree equation\[\left( {{b}^{2}}-{{a}^{2}} \right){{x}^{2}}+\left( {{c}^{2}}-{{b}^{2}} \right)x+\left( {{a}^{2}}-{{c}^{2}} \right)=0\]has equal roots, then which of the following conditions will necessarily be true?

    A)  \[\sum{{{a}^{2}}={{a}^{2}}{{b}^{2}}{{c}^{2}}}\]        

    B)  \[{{b}^{2}}+{{c}^{2}}={{a}^{2}}\]

    C)  \[{{b}^{2}}+{{c}^{2}}=2{{a}^{2}}\]       

    D)  \[{{(a+b+c)}^{2}}=ab+bc+ca\]

    Correct Answer: C

    Solution :

    (c): Trivial Solution is got by observance, put x = 1 and equation is satisfied. Hence x = 1 is a root: According to question, other root is also 1 \[\therefore \] sum of roots \[=1+1=2=\frac{-\left( {{c}^{2}}-{{b}^{2}} \right)}{\left( {{b}^{2}}-{{a}^{2}} \right)}\] \[\Rightarrow 2{{b}^{2}}-2{{a}^{2}}={{b}^{2}}-{{c}^{2}}\Rightarrow {{b}^{2}}+{{c}^{2}}=2{{a}^{2}}\] Product of roots \[=1\times 1=1=\frac{{{a}^{2}}-{{c}^{2}}}{{{b}^{2}}-{{a}^{2}}}\Rightarrow \] again \[{{b}^{2}}+{{c}^{2}}=2{{a}^{2}}\]        


You need to login to perform this action.
You will be redirected in 3 sec spinner