Question

determinar o valor de X para que a sequência (3+x, 5x, 2x+11) seja uma PA

Answer 1

$P.A.(a_1,a_2,a_3)\\ Em \ toda \ P.A.: \ \ a_2=\frac{a_1+a_3}{2}\\\\ P.A.(3+x,5x,2x+11)\\ 5x=\frac{3+x+2x+11}{2}\\ 10x=3+x+2x+11\\ 10x=3x+14\\ 10x-3x=14\\ 7x=14\\ x=\frac{14}{7}\\ x=2\\ E \ a \ P.A. \ formada: \\ P.A.(3+x,5x,2x+11)\\ P.A.(3+2,5.2,2.2+11)\\ P.A.(5,10,15)$