英语周报2020一2021七下仁爱版51答案

18.(本小题满分12分)(1)由已知,学生为优秀的概率为记优质学生数为X,由题意知,X的所有可能取值为0,1,2,3则P(X=0)=C3(0.4)=0064,P(X=1)=C1(0.4)20.6=0.288P(X=2)=C0.4(0.6)2=0.432,P(X=3)=C3(0.6)=0.216故X的分布列为0.0640.2880.430.216所以X的数学期望为E(X)=3×0.6=1.86分(2)填写列联表如下优秀学生非优秀学生合计甲方案乙方案合计120计算k2=12040×28-20×32)。22252.70660×60×72×48所以不能在犯错误的概率不超过0.1的前提下认为学生综合测试评分优秀与教学方案有关12分19.(本小题满分12分)(1)取AB中点为O,连结OD,OB,因为△ABA中BB=BA,所以OB⊥AB因为AB⊥B1D,OB∩BD=B,所以AB⊥平面BOD因为ODc平面BOD,所以AB⊥OD3分由已知,BC⊥BB,又OD∥BC,所以OD⊥BB1因为AB∩BB1=B,所以OD⊥平面ABBA又ODc平面ABC,所以平面ABC⊥平面ABBA(2)由(1)知,OB,OD,OB两两垂直.以O为坐标原点,OB的方向为x轴的方向,OD的方向为y轴的方向,OB的方向为2轴的方向,1OB为单位长度1,建立如图所示的空间直角坐标系O-xyz可知B.00,B10、3),D0.0),A-10.0),c(.2.0),c1(02,)则BB1=(-10,√3),BD=(0,-√3),B1A=(-10.-√3),CC=(-10.3)龙江考试-x+√3z=0B有即m=(√3,3,1)设平面BA的法向量为n=(x,y,z),则Bn·B1A=0x+√3z=0有{y=1,即n=(0.10)则cos(m,n)=11分所以二面DBB1一4的余弦值为y?712分0.(本小题满分12分)(1)因为焦点F以点A,B的坐标分别为所以S△AOB2p.=2,故P=2故抛物线C的方程为y2=4x.5分(2)由题设P(x,y),Q(x2y),易知直线的斜率存在,记为k则设直线l:y=kx+m,与y2=4x联立得ky2-4y+4m=0得y+y2=,H1y2=42mr,+xVy2黑龙江考试VI Jx1x2y1·y2mk+=互+卫2=52(6+m)+x(6+m)2+m(+)=4又知kop=tana,ko=tan4tan a+tantan(a+B)OAOBm -= tan -=lI-tan a tan B 1-kokor1 4k解得m=4k+4,所以直线l:y=kx+4k+4=k(x+4)+4,恒过定点(4,4)12分

第二节One possible wersionQuich, dets get some wet pawer toneis, " seid JudyEveryone sprang into action. Afler rubbing haid, ty namestill remained. I think I slw H can of cleaner by the sinkin thc coat room." I said as i raced to find it. We rubbedwith the cleaner and my name came off, but in the processof removing it. wc: left a friction Imark on the chulkbuurdHearing footsteps coning, we dried the wul urea as much aswe could with more paper towels.We were just slipping into our desks when the bell rengThe other students bewan entering the classroom. Theteacher walked in soon afterwards. Mrs. Eimer never askelabout the friction mark. Muybe she never nol iced il, lul Tdid. Every time I walked past the chalkboard, I remem-bered it. The lesson I leaned thot day is that"No one willever krow is never True, Even if no one else found out. Imyself knew. Sometimes living with, a guilty consciene ia

以上就是英语周报2020一2021七下仁爱版51答案，更多英语周报答案请关注本网站。