Respuesta :

devishri1977

Answer:

Step-by-step explanation:

Use Pythagorean theorem,

Base² + altitude² =hypotenuse²

x² + 19² = 21²

x² + 361 = 441

         x² = 441 - 361

          x² = 80

          [tex]x =\sqrt{80}=\sqrt{2*2*2*2*5}=2*2*\sqrt{5}=4\sqrt{5}[/tex]