6 / (х-6)(х+6) + 6 / (х+6)² + 1 / 2(х+6) = 0
6*2(х+6)+6*2(х-6)+1*(х-6)(х+6) / 2(х-6)(х+6)² = 0
12х+72+12х-72+х²-36 / 2(х-6)(х+6)² = 0
х²+24х-36 / 2(х-6)(х+6)² = 0
ОДЗ: 2(х-6)(х+6)²≠0; х≠ -6; 6
х²+24х-36=0
D= 576+144=720
х₁ = -24-√720 / 2 = -24-12√5 / 2 = 2(-12-6√5) / 2 = -12-6√5
х₂ = -24+√720 / 2 = -24+12√5 / 2 = 2(-12+6√5) / 2 = -12+6√5
A₁₉=a₁+d(19-1)
a₁₉=9+3×18
a₁₉=63
Удачи!