Question

Calcule o valor de X. ​

Answer 1

Resposta:

1)

a)

$x \times 4 = 9 \times 5 \\ \\ 4x = 45 \\ \\ \blue{x = \dfrac{45}{4} }$

b)

$11 \times 2 = 9 \times x \\ \\ 22 = 9x \\ \\ 9x = 22 \\ \\ \blue{x = \dfrac{22}{9} }$

c)

$9 \times 2 = 2x \times x \\ \\ 18 = 2 {x}^{1 + 1} \\ \\ 18 = {2x}^{2} \\ \\ {x}^{2} = \dfrac{18}{2} \\ \\ {x}^{2} = 9 \\ \\ x = \pm \sqrt{9 } \\ \\ \blue{x = + 3 \: Pois \: é \: Comprimento.}$

d)

$(x + 12) \times 1 = x \times x \\ \\ x + 12 = {x}^{1 + 1} \\ \\ x + 12 = {x}^{2} \\ \\ \\ \\ {x}^{2} = x + 12 \\ \\ {x}^{2} - x - 12 = 0 \\ \\ \Delta = {b}^{2} - 4ac \\ \\ \Delta = ( - {1)}^{2} - 4(1)( - 12) \\ \\ \Delta = 1 + 48 \\ \\ \Delta = 49 \\ \\ Bhaskara \\ \\ \dfrac{ - b \pm \sqrt{ \Delta} }{2 a } \\ \\ \dfrac{ - ( - 1 )\pm \sqrt{49} }{2(1)} \\ \\ \dfrac{1 \pm 7}{2} \\ \\ x1 = \dfrac{1 + 7}{2} \\ \\ x1= \frac{8}{2} \\ \\ \blue{ x1 = 4} \\ \\ x2 = \dfrac{1 - 7}{2} \\ \\ x2 = - \dfrac{ 6}{2} \\ \\ x2 = - 3 \: (Descartamos, \:pois \:é \:comprimento)$

Bons Estudos!