等差数列中,a1=3,a100=36,则a3+a98=

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等差数列中,a1=3,a100=36,则a3+a98=

等差数列中,a1=3,a100=36,则a3+a98=
等差数列中,a1=3,a100=36,则a3+a98=

等差数列中,a1=3,a100=36,则a3+a98=
a3=a1+2d (d为公差)
a100=a98+2d(即:a98=a100-2d)
∴a3+a98=a1+2d +a100-2d
=a1+a100
=39

a3+a98=a1+a100=3+36=39

等差数列有这个性质,若m+n=p+q,则am+an=ap+aq,故a1+a100=a3+a98=3+36=39

a1+a100=a2+a99=a3+a98=39