4-2.Quadratic Equations and Inequations
hard

જો $a, b, c$ એ ત્રિકોણની ત્રણ બાજુઓ છે. જે $\left(a^2+\right.$ $\left.b^2\right) x^2-2 b(a+c) \cdot x+\left(b^2+c^2\right)=0$ નું સમાધાન કરે છે. જો $x$ ના શક્ય ઉકેલોનો ગણ $(\alpha, \beta)$ છે. તો $12\left(\alpha^2+\beta^2\right)=$............................

A

$30$

B

$36$

C

$35$

D

$37$

(JEE MAIN-2024)

Solution

$\left(a^2+b^2\right) x^2-2 b(a+c) x+b^2+c^2=0 $

$ \Rightarrow a^2 x^2-2 a b x+b^2+b^2 x^2-2 b c x+c^2=0$

$ \Rightarrow(a x-b)^2+(b x-c)^2=0 $

$ \Rightarrow a x-b=0, \quad b x-c=0 $

$ \Rightarrow a+b>c \quad b+c>a \quad \quad c+a>b$

$a+a x>b x $

$a+a x > a x^2 $

$ x^2-x-1 < 0$

$a x+b x > a $

$ a x+a x^2 > a $

$ x^2+x-1 > 0$

$a x^2+a>a x$

$x^2-x+1>0$

always true

$\frac{1-\sqrt{5}}{2}<\mathrm{x}<\frac{1+\sqrt{5}}{2}$

$\mathrm{x}<\frac{-1-\sqrt{5}}{2}, \text { or } \mathrm{x}>\frac{-1+\sqrt{5}}{2} $

$\Rightarrow \frac{\sqrt{5}-1}{2} < x < \frac{\sqrt{5}+1}{2}$

$\Rightarrow \alpha=\frac{\sqrt{5}-1}{2}, \beta=\frac{\sqrt{5}+1}{2}$

$12\left(\alpha^2+\beta^2\right)=12\left(\frac{(\sqrt{5}-1)^2+(\sqrt{5}+1)^2}{4}\right)=36$

Standard 11
Mathematics

Similar Questions

Start a Free Trial Now

Confusing about what to choose? Our team will schedule a demo shortly.