Question

Y²+4y-21=0 respostas??

Answer 1

Use a fórmula de Bhaskara:

$x = \frac{ - b \frac{ + }{ - } \sqrt{ {b}^{2} - 4ac } } {2a}$

$x = \frac{ - (4) \frac{ + }{ - } \sqrt{ {4}^{2} - 4 \times 1 \times (- 21)} }{2 \times 1}$

$x = \frac{ - 4 \frac{ + }{ - } \sqrt{16 + 84} }{2}$

$x = \frac{ - 4 \frac{ + }{ - } \sqrt{100} }{2}$

$x = \frac{ - 4 \frac{ + }{ - }10 }{2}$

$x1 = \frac{ - 4 + 10}{2} = 3$

$x2 = \frac{ - 4 - 10}{2} = - 7$