∵在数列{a[n]}中,a[1]=1,a[n+1]=a[n]+c(c为常数,n为正整数）∴a[n+1]-a[n]=c,数列{a[n]}是首项为1,公差为c的等差数列即：a[n]=1+c(n-1)∵a[1],a[2],a[5]成公比不为一的等比数列∴a[2]^2=a[1]a[5]即：(1+c)^2=1+4c解...