1.求下列函数的极值:-|||-(1) =2(x)^3-6(x)^2-18x+7 ;-|||-(2) =x-ln (1+x) ;-|||-(3) =-(x)^4+2(x)^2 ;-|||-(4) =x+sqrt (1-x) ;-|||-(5) =dfrac (1+3x)(sqrt {4+5{x)^2}} ;-|||-(6) =dfrac (3{x)^2+4x+4}({x)^2+x+1} ;-|||-(7) =(e)^xcos x ;-|||-(8) =(x)^dfrac (1{x)} ;-|||-(9) =3-2((x+1))^dfrac (1{3)}-|||-;(10) =x+tan x .