设{an}是一个公差为d（d不等于0）的等差数列，它的前10项和S10=110，且a1,a2,a4成等比数列。(1)证明a1=d
热心网友
{an}是一个公差为d（d不等于0）的等差数列，a1,a2,a4成等比数列==(a1+d)(a1+d)=a1(a1+3d)==a1^2+2a1d+d^2=a1^2+3a1d==2a1+d=3a1==a1=d
热心网友
由a1,a2,a4成等比数列得:a1*a4=a2*a2 == a1(a1+3d)=(a1+d)(a1+d) ==a1=d
设{an}是一个公差为d（d不等于0）的等差数列，它的前10项和S10=110，且a1,a2,a4成等比数列。(1)证明a1=d
{an}是一个公差为d（d不等于0）的等差数列，a1,a2,a4成等比数列==(a1+d)(a1+d)=a1(a1+3d)==a1^2+2a1d+d^2=a1^2+3a1d==2a1+d=3a1==a1=d
由a1,a2,a4成等比数列得:a1*a4=a2*a2 == a1(a1+3d)=(a1+d)(a1+d) ==a1=d