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प्रश्न
Solve the following quadratic equation by factorisation.
x2 + x – 20 = 0
उत्तर
x2 + x – 20 = 0
\[\Rightarrow x^2 + 5x - 4x - 20 = 0\]
\[ \Rightarrow x\left( x + 5 \right) - 4\left( x + 5 \right) = 0\]
\[ \Rightarrow \left( x - 4 \right)\left( x + 5 \right) = 0\]
\[ \Rightarrow \left( x - 4 \right) = 0 \text{ or } \left( x + 5 \right) = 0\]
\[ \Rightarrow x = 4 \text{ or} x = - 5\]
So, 4 and \[-5\] are the roots of the given quadratic equation.
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