2021-2022英语周报高一课标综合OT第45期答案

Passage 5When the earthquake was happened in 2008 my auntwas still a little girl in A small county in Sichuan. Todayashe can wel remember doctors and nurses in whiteovcrallhiwere busy day and night savc thewho/thatsavinginured in our hometown. It was then when she made uher mind to be someone like them. Her drcam came trulyfter she graduated from a local medical school. On1rJanuary 2020, when bad news came that Hubei was badlyin need of doctors and nurses to fight COVID-19, sheapplied to be there to help out but her application wasapproved. Before she leaves, she told us she was gratefuleltfor what people did for us after the earthquake and thatshe had decided to pay them forward.

19.【解析】(1)P是抛物线E:y2=4x上的动点，F是抛物线E的焦点(1,0)，准线方程为x=一1，由抛物线的定义可得PF|=d=xp十1，由xp≥0，可得d的最小值为1，PF的最小值为1；…(5分)(2)设B(0,m),C(0,n),P(x,yo),6=4xo,则PB的方程为y=山一mx十m,PC的方程为y=凸二”x十n,(6分)由直线PB与圆(x一1)2十y=1相切，可得0一m十m.xo(7分)/x6+(yo一m)整理得(x一2)m2十2y%m一x=0,同理可得(x-2)n2十2yon-x=0,..................(8分)即有m,n为方程(x一2)x2十2ox一x=0的两根，可得m十n=20,mn一2-x0To2-x04y6则m-l=√(m+n)-4mm=√(2-4x0/4.x6+8.x2-x0(10分)由PF∈[4,6]，可得x+1∈[4,6]，即x∈[3,5]，令t=2-x=x-2,t∈[1,3]，即有1m-n=√4(2+)+8(2+D2入+日+1在[1,3]递减，…(11分)可得=3，即x=5时，BC=m-m取得最小值23宽…(12分)

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