初中数学题

初中数学题 --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- 某房地产产产公司准产利用一产产400米.产300米的产方形地产建一住宅小～产在中产建造正方形群～小角产商产～其余均产产地～其中要求商产产面产占群面产个区划楼区两辟两个区区楼的九分之一～产地面产占小面产的一半～产求出可建群占地的正方形产产～出的产产产。区楼并画你解,产群所占面产产产产楼a 因产产地面产占1\2 所以商产面产加群面产占区楼1\2 而商产面产占群面产的区楼1\922 可得,a+1\9a=1\2*400*300 解得,a=60?15 ---------------------------------------------------------------------------------------------------------------------------------------------------------------2已知|2m-3|=1～产解产于x的方程3mx;x+1,-5;x+1,;x-1,=x. 222解,原式=3mx+3mx-5x+5=x2产(3m-6)x+3mx+5=0根据|2m-3|=1解得m=2或m=1当m=2产,原式=6x+5=0,x=-5/6当m=1产,2原式=-3x+3x+5=0x=(3??69)/6 ---------------------------------------------------------------------------------------------------------------------------------------------------------------已知Rt三角形的周产产2+?6～斜产中产产产1～求三角形ABC的面产 由斜产的中产产1～得出斜产产产2.产直角产分产产两条x y有x+y+2=2+?622x+y=422解方程的产候注意～将x+y=?6～产同产平方～得到两x+y+2xy=622将x+y=4产入得～xy=1 面产=xy/2=1/2 --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- 广安市某楼准以盘盘盘盘盘盘盘平方米每6000元的均价外售,由于国院有房地的新政策出台后,房者持望,房地商了加盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘快金周,价格两次下后,决定以盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘平方米每4860元的均价售,盘盘盘盘盘，1,求平均次下的百分率,每盘盘盘盘盘盘，2,某人准以价均价一套盘盘盘盘盘盘盘盘盘盘盘100平方米的住房,商予以下两惠方案以供:?打盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘9.8折售,?不打折,一次性送装修盘盘盘盘盘平方米每80元,哪盘盘盘盘方案更惠,盘盘盘解:，1盘盘盘盘盘盘盘盘盘,平均次下的百分率x每,盘,解得或，舍去,,故平均次下的百分率每盘盘盘盘盘盘10%, ，2,方案?盘盘盘盘房惠:4860×100×0.02=9720，元,方案?盘盘盘盘房惠:80×100=8000，元,,故方案?盘盘盘盘更惠,盘盘盘 --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------如产梯形ABCD中,AD//BC,AB=CD,?B=60?,AD=10,BC=18,求梯形的周产 产A作高AFBF=;BC-AD,/2=4?B=60?～AB=2BF=8周产=2AB+BC+AD=16+10+18=44 ---------------------------------------------------------------------------------------------------------------------------------------------------------------如,在梯形盘盘盘盘盘ABCD中,AD?BC,AD=6,BC=16,E是BC的中点,点P以秒每1个位度的速度从点盘盘盘盘盘盘盘盘盘A出,沿盘盘盘AD向点D运,点盘盘盘Q同以秒盘盘每2个位度的盘盘盘盘盘速度从点C出,沿盘盘盘CB向点B运,点盘盘盘P停止运,点盘盘盘盘Q也随之停止运,当运盘盘盘盘盘盘盘 2 或 143 秒,以点盘盘盘盘 P,Q,E,D盘盘盘盘盘盘盘盘盘盘盘点的四形是平行四形,解:由已知梯形,，1,当Q运到盘盘E和B之,运盘盘盘盘盘盘盘盘t,得:盘盘盘2t,162=6,t,解得:t=143,，2,当Q运到盘盘E和C之,运盘盘盘盘盘盘盘盘t,得:盘盘盘162,2t=6,t,解得:t=2,故:盘盘2或143, --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- ，1,产法1:在Rt?EBC中,M是斜盘EC的中点,?, 在Rt?EDC中,M是斜盘EC的中点,?, ? BM=DM,且点B、C、D、E在以点M盘盘心、BM盘盘盘半径的上,?? BMD=2?ACB=90?,即BM?DM, 产法2:明盘盘BM=DM与法盘盘1相同,下面明盘盘BM?DM,? DM=MC,?? EMD=2?ECD,? BM=MC,?? EMB=2?ECB,?? EMD，?EMB =2，?ECD，ECB,,?? ECD，?ECB=?ACB=45?,?? BMD=2?ACB=90?,即BM?DM, ，2,当?ADE盘点A逆旋小于盘盘盘盘盘盘45?的角盘,，1,中的成立,盘盘盘盘 盘明如下:产法1，利用平行四形和全等三角形,:盘盘盘盘盘盘盘盘盘盘盘盘BD,延盘DM至点F,使得DM=MF,盘盘BF、FC,延盘ED交AC于点H,? DM=MF,EM=MC,?四形 盘盘CDEF盘盘盘平行四形.? DE?CF ,ED =CF.? ED= AD,? AD=CF.? DE?CF,?? AHE=?ACF, M D B A C E H F? ,,?? BAD=?BCF.又?AB= BC,? ?ABD??CBF.? BD=BF,?ABD=?CBF.?? ABD+?DBC =?CBF+?DBC,??DBF=?ABC =90?.在Rt?中,由,,得BM=DM且BM?DM, M D B A C E 产法2，利用旋,:盘盘盘盘盘盘盘BD,将?ABD盘点B逆旋盘盘盘盘90?,点A旋到点盘盘盘C,点D旋到点,得到?,盘盘盘盘盘盘盘且,盘盘,??, 又?,?四形平行四形, 盘盘盘盘盘盘盘盘盘? D、M、三点共,且,盘盘盘在Rt?中,由,,得BM=DM且BM?DM, M D B A C E H 产法3，利用旋,:盘盘盘盘盘盘盘BD,将?ABD盘点B逆旋盘盘盘盘90?,点A旋到点盘盘盘C,点D旋到点,得到盘盘盘盘盘盘?,且,盘盘盘盘盘,延ED交AC于点H,?? AHD= 90?,?DAH= 90?,(45?,?BAD)= 45?，?BAD,,?,?,?,又?, ?四形平行四形,? 盘盘盘盘盘盘盘盘盘盘 D、M、三点共,且,盘盘盘在Rt?中,由,,得BM=DM且BM?DM, --------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------222已知,如产,在四产形ABCD中,?ABC=90?,CD?AD,AC+CD=2AB.(1)求产:AB=BC (2)当BE?AD于E产～产产明BE=AE+CD;1,产明,产接AC,??ABC=90?～222?AB+BC=AC,?CD?AD～222?AD+CD=AC,222?AD+CD=2AB～222?AB+BC=2AB～?AB=BC,;2,产明,产C作CF?BE于F,?BE?AD～?四产形CDEF是矩形,?CD=EF,??ABE+?BAE=90?～?ABE+?CBF=90?～??BAE=?CBF～?在?BAE与?CBF中??BAE??CBF,;AAS,?AE=BF,?BE=BF+EF=AE+CD, ---------------------------------------------------------------------------------------------------------------------------------------------------------------如产,在平行四产形ABCD中,AC,BD相交于点O,AE?BC,垂足产E,EO的延产产交AD于点F.求产,四产形 AECF产矩形解,四产形AECF产矩形?ABCD四产形?AO=OC,?OAF=?OCE,AF//CE??AOF=?COE??AOF??COE?AF=CE?四产形AECF产平行四产形?AE?EC ?四产形AECF产矩形 --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- ，1,明盘盘:由折叠可知,AF,CF,AO,CO. O A B D E F C P?在矩形ABCD中AD?CF,??OAE,?OCF,?OEA,?OFC,??AOE??COF(AAS).?AE,CF.?四形盘盘AFCE是平行四形盘盘.(一平行且相等的四形是平行四形盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘盘)?四形盘盘AFCE是菱形(一相等的平行四形是菱形盘盘盘盘盘盘盘盘盘盘盘盘盘盘).，2,解:由，1,可知AF,AE,10cm.??ABF是直角三角形,222?AF,AB，BF,100,AB?BF,24,?AB，BF,14,即?ABF的周盘盘24cm.2，3,解:在段盘盘AC上存在一点P,使得2AE,AC?AP.如盘,盘点E作EP?AD交AC于点P,?AC?EF,?Rt?AOE?Rt?AEP22?AE,AO?AP,AC?AP,即2AE,AC?AP. ---------------------------------------------------------------------------------------------------------------------------------------------------------------根据下面三产产建造的建筑物是什产产子的,共有产,一共需要多少小正方,几个体 答:共三,需盘盘盘9个小正方体。 --------------------------------------------------------------------------------------------------------------------------------------------------------------- 根据要求出下列立产形的产产。画体 --------------------------------------------------------------------------------------------------------------------------------------------------------------- 画出右方产物的三产产。 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解:盘C，x,y,,?四形盘盘ABCD是矩形,点A的坐，盘盘盘盘2,盘2,,?B，盘2,y,、D，x,盘2,,?矩形ABCD的角盘盘盘BD盘盘盘盘盘盘坐原点,?y2,,=,2x,即xy=4,?又?点C在反比例函数yk22k1x=++的象上,盘盘盘盘2?xy=k+2k+1,?由??,得2k+2k,3=0,即，k,1,，k+3,=0,?k=1或k=,3,?k，0,?k=1,故盘A, --------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------22a?-7a-14a取些产产哪y/2a+3a=1/x次方是反比例函数?解析式?2a?-7a-14解:将原式整理:盘盘y=(2a?+3a),x 可以得到:?2a?+3a?0?2a?-7a-15=0解得a?0 a?-1.5 a=5 a=-1.5所以a=5所以解析式盘:y=65,x --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- 一次产产～某校有数学400名生加～抽出学参20名生的成产如下,学数学 85 75 89 90 85 78 94 88 83 66 72 71 85 86 96 80 98 87 62 92 ;1,下面的产率分布表填写 ;1, 分产产累产数产数产率 60.5~70.520.10 70.5~80.550.25正 80.5~90.590.45正 90.5~100.540.20 20201.00合产 ;2,成产80分以上的人产产数260人～占全校的65% --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------- ，1,易求得, , 因此得.盘(2)易得?盘盘盘,且相似比,得盘盘盘盘.，3,120?, ---------------------------------------------------------------------------------------------------------------------------------------------------------------如产1～已知～矩形ABCD的产AD=3～产角产产产5～矩形将ABCD置于直角坐产系～点内C原点与O重合～点D在x产正 产上～且反比例函的产像的一分支位于第一象限数个。;1,求产1中～点A的坐产是多少,;2,若矩形ABCD从产1的位置产始沿x产的正方向移产～每秒移产1个产位～1秒后点A产好落在反比例函的产像上～如产数2～求反比例函的表式。数达解,;1,?矩形ABCD的产AD=3～产角产产产5 ?AB=?AC?-AD?=4 ?点C与原点O重合 ?A;4,3, ;2,?矩形ABCD从产1的位置产始沿x产的正方向移产～每秒移产1个产位 ?1秒后点A;5,3, 产产反比例函的表式产,数达y=k,x ?1秒后点A产好落在产反比例函的产像上数 ?把点A;5,3,代入y=k,x得,k=15 ?产反比例函的表式产,数达y=15,x答,;1,点A;5,3,～;2,产反比例函的表式产,数达y=15,x。 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