equaçôes logaritimas

obtenha quadragismo sendo da PA sendo                                                                  r=5                                                                                                                                a12=-8                                                                                                                         a46= ?                            a46=a12+34r                                                                                                                   a46=-8+34.5                                                                                                                  a46=-8+170                                                                                                                    a46=162