Question

using formula method find x 3x2 + 2root5x -5=0?

Answer 1

$= \frac{ - b + - \sqrt{( {b)}^{2} - 4ac } }{2a} \\ a = 3 \\ b = 2 \sqrt{5} \\ c = - 5 \\ = \frac{ - 2 \sqrt{5} + - \sqrt{( {2 \sqrt{5} ) }^{2} - 4(3)( - 5)} }{6 } \\ = \frac{ - 2 \sqrt{5} + - \sqrt{20 + 60} }{6} \\ = \frac{ - 2 \sqrt{5} + - \sqrt{80} }{6} \\ = \frac{ - 2 \sqrt{5} + - 4 \sqrt{5} }{6} \\ x1 = \frac{ - 2 \sqrt{5} + 4 \sqrt{5} }{6} \\ = \frac{2 \sqrt{5} }{6} = \frac{ \sqrt{5} }{3} \\ x2 = \frac{ - 2 \sqrt{5} - 4 \sqrt{5} }{6} \\ = \frac{ - 6 \sqrt{5} }{ 6 } \\ = - \sqrt{5}$