Решите уравнение
log3 x+log3 x^2=-1

loqa b+ loga c=loga b*c

log3 x*x²=- 1
log3 x³=-1
x³=3^(-1)=1/3
x=∛(1/3)=1/∛3

проверка 
log3 (1/∛3)+ log3 (1/∛3)²=-1/3-2/3=-3/3=-1