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NCERT Class XI Mathematics - Complex Numbers and Quadratic Equations - Solutions

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Question : 32 of 52
Marks: +1, -0
x2+x2x^2 + \frac{x}{\sqrt{2}} + 1 = 0
Solution:  
We have , x2+x2x^2 + \frac{x}{\sqrt{2}} + 1 = 0
Comparing the given equation with the general form ax2ax^2 + bx + c = 0,
we get a = 1 , b = 12\frac{1}{\sqrt{2}} , c = 1
∴ x = b±b24ac2a\frac{-b \pm \sqrt{b^2 - 4ac}}{2a} = 12±(12)24×1×12.1\frac{-\frac{1}{\sqrt{2}} \pm \sqrt{\left(\frac{1}{\sqrt{2}}\right)^2 - 4 \times 1 \times 1}}{2.1} = 12+1242\frac{-\frac{1}{\sqrt{2}} + \sqrt{\frac{1}{2} - 4}}{2}
= 12±1822\frac{-\frac{1}{2} \pm \sqrt{\frac{1 - 8}{2}}}{2} = 12±722\frac{-\frac{1}{\sqrt{2}} \pm \sqrt{-\frac{7}{2}}}{2} = 1±i722\frac{-1 \pm i\sqrt{7}}{2\sqrt{2}}
∴ The roots of the given equation are 1+i722\frac{-1 + i\sqrt{7}}{2\sqrt{2}} and 1i722\frac{-1 - i\sqrt{7}}{2\sqrt{2}}
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