Question

alguem sabe fazer o calculo dessa conta ? x2-9x- 20=0?

Answer 1

Olá!

${x}^{2} - 9x - 20 = 0$

$a = 1 \\ b = ( - 9) \\ c = ( - 20)$

$\Delta = {b}^{2} - 4ac \\ \Delta = {( - 9)}^{2} - 4 \times 1 \times ( - 20) \\ \Delta = 81 + 80 \\ \Delta = 161$

$x = \frac{ - b\pm \sqrt{\Delta} }{2a} \\ \\ x = \frac{ - ( - 9)\pm \sqrt{161} }{2 \times 1} \\ \\ x = \frac{9\pm \sqrt{161} }{2}$

$x_{1} = \frac{9 + \sqrt{161} }{2} \\ \\ x_{2} = \frac{9 - \sqrt{161} }{2}$

$S = \{ \frac{9 - \sqrt{161} }{2} , \: \frac{9 + \sqrt{161} }{2} \}$

Espero ter ajudado! :)