[tex]\frac{13}{x} =\frac{x}{13} \\x^2=13^2\\x=\sqrt{13^2} =13\\x_2=-13[/tex]
[tex]\frac{5x}{4} =\frac{20}{x} \\5x^2=20*4\\5x^2=80\\x^2=\frac{80}{5} \\x^2=16\\x_1=\sqrt{16} =4\\x_2=-\sqrt{16} =-4[/tex]
[tex]\frac{3-x^2}{16} =\frac{1}{8} \\8(3-x^2)=16\\24-8x^2=16\\-8x^2=16-24\\-8x^2=-8 |*(-1)\\8x^2=8\\x^2=\frac{8}{8} =1\\x_1=\sqrt{1} =1\\x_2=-\sqrt{1} =-1[/tex]
[tex]\frac{3x}{2} =\frac{2}{3x} \\(3x)^2=2^2\\3^2x^2=4\\9x^2=4\\x^2=\frac{4}{9} \\x_1=\sqrt{\frac{4}{9}} =\frac{2}{3} \\x_2=-\sqrt{\frac{4}{9}} =-\frac{2}{3}[/tex]
