Log 1/7(9-x)=-2 решите

Question

Log 1/7(9-x)=-2
решите

Answer 1

Log1/7 (9-x)=-2*log1/7 (1/7)
 log1/7 (9-x)=log1/7 (1/7)^-2
 log1/7 (9-x)=log1/7 7^2
  9-x=49
  -x=49-9
 x=-40