Question

x2-x-20=0 by completing square method​

Answer 1

$x {}^{2} - x - 20 = 0 \\ = > (x) {}^{2} - 2 \times x \times \frac{1}{2} + ( \frac{1}{2} ) {}^{2} - 20 = ( \frac{1}{2} ) {}^{2} \\ = > (x - \frac{1}{2}) {}^{2} - 20 = \frac{1}{4} \\ = > (x - \frac{1}{2}) {}^{2} = \frac{1}{4} + 20 \\ = > (x - \frac{1}{2} ) {}^{2} = \frac{1 + 80}{4} \\ = > (x - \frac{1}{2} ) {}^{2} = \frac{81}{4} \\ = > x - \frac{1}{2} = ( + - )\sqrt{ \frac{81}{4} } \\ = > x - \frac{1}{2} = ( + - ) \frac{9}{2} \\ = > x = \frac{1}{2} ( + - ) \frac{9}{2} \\ = > x = \frac{1( + - )9}{ 2} \\ = > x = \frac{1 + 9}{2} \: or \: x = \frac{1 - 9}{2} \\ = > x = \frac{10}{2} \: or \: x = \frac{ - 8}{2} \\ = > x = 5 \: or \: x = - 4 \: ans...$

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