Question

Valendo 14 pontos : ABRA A IMAGEM

Answer 1

a)
$y = {x}^{2} - 3x - 10 \\ {b}^{2} - 4ac = {( - 3)}^{2} - 4 \times 1 \times ( - 10) = 9 + 40 = 49 \\ \sqrt{49} = 7 \\ \\ x = \frac{ - ( - 3) + \sqrt{49} }{2 \times 1} \\ x = \frac{3 + 7}{2} \\ x = 5 \\ \\ x = \frac{ - ( - 3) - \sqrt{49} }{2 \times 1} \\ x = \frac{3 - 7}{2} \\ x = \frac{ - 4}{2} = \frac{ - 2}{1}$

b)
$f(x) = {5x}^{2} + 15x \\ {5x}^{2} + 15x = 0 \\ 5x(x + 3 ) = 0 \\ x = 0 \\ x + 3 \\ x = - 3$
c)
$y = { - 2x}^{2} + 8x \\ { - 2x}^{2} + 8x = 0 \\ 2x( - x + 4) = 0 \\ x = 0 \\ \\ - x + 4 = 0 \\ - x = - 4 \\ x = 4$