2022英语周报初二16期答案

19.【解析】(1)由a1=1可得2·a1=2,又2a4-23a1=22(2a4-a)=1,(3分){2a}是首项为2,公差为1的等差数列,故2a=2+(7-1)=n+1{a}的通项公式为a,=”+:(6分)(2)(理)由(1)可得5.=2222①-②可得S1+++22x0-y)n+123m+3n+1=3.们+3(10分)则a+S=+1+32°3刀+3由,+S,532可得n≤6,故正整数n的最大值为6.(12分)(2)(文)由(1)可得S,=2+3+4++n+11s=2+3①-②可得5=1+,=1+13n+32122S=3、+3(12分)

二、读后续写范文(满分25分)Possible version 1Paragraph 1:It was time to put an end to the Magic Marty show. I walked over. "It was fishing line. " I sneeredfolding my arms. Marty subconsciously fingered the fishing line and nervously whispered, "So, are yougoing to tell people? Seeing the panic in his eyes, somehow, I hesitated. Should I_reveal the secret, Martymight lose his new_ friends. Finally, after struggling for a moment, I replied, "Nah, I won't say anythingMarty let out a relieved sigh, and I turned to walk awayParagraph 2Waitr"Marty jumped in front of me. Unexpectedly, he patted my arm, grinning. "You' ve got a prettygood eye for magic. Want to join me? "I nodded joy fully. That's how the Magic Marty and MysteriousMatt Lunch Show began. Now we've been a magic team for three months. And since I became a fellowmagician, Marty has let me in on some of his other tricks. It turns out that instead of a fake magician, Martyis a real friend.(150 words

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