Question

calcule n, sabendo ue a1=2, r=3/2 e an=20

Answer 1

$a_{n} =20\\\\a_{1} =2\\\\r= \frac{3}{2}\\\\n=? \\\\\\ a_{n} = a_{1} +(n-1)*r\to \\\\\\20=2+(n-1)* \frac{3}{2}\to \\\\20=2+ \frac{3}{2}n- \frac{3}{2}\to \\\\ 20-2+ \frac{3}{2}= \frac{3}{2}n\to \\\\ mmc=2 \\\\ 40-4+3=3n\to \\\\ 39=3n\to \\\\ \frac{39}{n} \to \\\\n=13$