Question

Determinati x aparține R din proportiile 13/x=x/13

Answer 1

$\frac{13}{x} = \frac{x}{13}$

$x \times x = 13 \times 13$

${x}^{2} = 169$

$x = \pm \sqrt{169}$

$x = \pm13$

Answer 2

$\frac{13}{x} = \frac{x}{13} \\ x ^{2} = 13^{2} \\ {x}^{2} = 169 \\ {x}^{2} - 169 = 0 \\ {x}^{2} - {13}^{2} = 0 \\ (x - 13)(x + 13) = 0 \\ x - 13 = 0 = > x = - 13 \\ x + 13 = 0 = > x = 13$
S={13,-13}