1.用第一类换元法求下列积分:-|||-(1) int ((3x+2))^20dx ;-|||-(2) int (10)^3xdx;-|||-(3) int dfrac (1)(sqrt [3]{1-2x)}dx;-|||-(4)|sin4xdx;-|||-(5) int dfrac ({e)^x}({e)^x+2}dx;-|||-__-|||-(6) int sqrt (2+sin x)cos xdx;-|||-(7) int dfrac (sin x)(1+{cos )^2x}dx;-|||-(8) int dfrac (xdx)(sqrt {{x)^2+1}};-|||-(9)|e^xcose^xdx;-|||-(10) int tan dfrac (x)(2)dx;-|||-(11) int dfrac (1)(sqrt {x)}sin sqrt (x)dx;-|||-(12) int dfrac (1)({x)^2}cos dfrac (1)(x)dx ;-|||-(10.1)(n)^2x