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

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Question : 28 of 52
Marks: +1, -0
x2x^2 - x + 2 = 0
Solution:  
We have , x2x^2 - x + 2 = 0
Comparing the given equation with the general form ax2ax^2 + bx + c = 0,
we get a = 1, b = –1, c = 2.
∴ x = b±b24ac2a\frac{-b\pm\sqrt{b^2-4ac}}{2a} = 1±(1)24×1×22\frac{1\pm\sqrt{(-1)^2-4\times1\times2}}{2} = 1±182\frac{1\pm\sqrt{1-8}}{2}
= 1±72\frac{1\pm\sqrt{-7}}{2} = 1±i72\frac{1\pm i\sqrt{7}}{2}
∴ The roots of the given equation are 1+i72\frac{1+i\sqrt{7}}{2} and 1i72\frac{1-i\sqrt{7}}{2}
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