Question

Preciso de ajudar rápido

Answer 1

a)

$- {x}^{2} + 4x + 5 \\ delta = {b}^{2} - 4 \times a \times c \\ {(4)}^{2} - 4 \times ( - 1 ) \times (5) \\ 16 + 20 = 36 \\ \frac{ - b + - \sqrt{delta} }{2 \times a} \\ \frac{ - 4 + - \sqrt{36} }{ - 2} \\ x1 = \frac{ - 4 + 6}{ - 2} = \frac{2}{ - 2} = - 1 \\ x2 = \frac{ - 4 - 6}{ - 2} = \frac{ - 10}{ - 2} = 5$

b)

${x}^{2} - 3x = 0 \\ x \times (x - 3) = 0 \\ x1 = 0 \\ x - 3 = 0 \\ x2 = 3$

c)

${2x}^{2} - 72 = 0 (\div )2 \\ {x}^{2} - 36 = 0 \\ {x}^{2} = 36 \\ x = + - \sqrt{36} \\ x1 = 6 \\ x2 = - 6$

d)

${x}^{2} + 10x + 25 \\ {b}^{2} - 4 \times a \times c \\ {(10)}^{2} - 4 \times 1 \times 25 \\ 100 - 100 = 0 \\ x = \frac{ - 10}{2} = - 5$