u=2x+1 ,x=(u-1)/2
f(u)=(u-1)^+6(u-1)-1=u^-2u+1+6u-6-1=u^+4u-6
f(x)=x^+4x-6有个地方是不是写错了。f(t)=(t-1)^+3(t-1)-1 x=t-1/2嘛。乘上6不是等于3(t-1)嘛。怎么是6(t-1)呢话说我习惯用t 呵呵