2019-2020学年北京市丰台区中考数学二模试?有标准答? - 百度文库 ϵͷ

ʱ : 2019-2020学年北京市丰台区中考数学二模试?有标准答? - 百度文库ϿʼĶ

...

㡿ʵ㣻ָݣָݣǵǺֵ

ԭʽָݡָݷǵǺֵԼֵĴ廯򣬼㼴ɵõ 𡿽⣺ԭʽ=42+1+2

18֪4x=3yʽx2y2xyx+y2y2ֵ 㡿ʽĻ㡪ֵ

ƽʽȫƽʽ㣬һϲô𰸼ɣ 𡿽⣺x2y2xyx+y2y2 =x24xy+4y2x2y22y2 =4xy+3y2 =y4x3y 4x=3y ԭʽ=0

19֪xһԪηx2+3x+1m=0ȵʵ 1mȡֵΧ

2mΪʱ̵ĸ 㡿бʽ

1ɷʵɵb24ac0ݼɵómһԪһβʽⲻʽɵóۣ

2mΪԼ1Ľۿɵómֵԭ̣÷ֽʽ̼ⷽɵóۣ

𡿽⣺1߹xһԪηx2+3x+1m=0ȵʵ =b24ac=3241m0 5+4m0ãm mȡֵΧΪm 2mΪm m=1

m=1ԭ̵ãx2+3x+2=x+10x+2=0

...

=4+2

...

ãx1=1x2=2

ʵm=1ʱ˷̵ĸΪx1=1x2=2

20ͼABCǵȱΣBDACڵDEΪBCе㣬DE֤DE=DC

㡿ȱεʣ

ݵȱεʵõAC=BCCD=ACBDC=90㣬ֱεʵõDE=BCǵõۣ

𡿽⣺ߡABCǵȱΣ AC=BC BDACڵD CD=ACBDC=90㣬 EΪBCе㣬 DE=BC DE=DC

212016529գ԰԰ӭˡս100һܡٹ·£̹10010ˡ10ķʽչһܰߣԭÿӼܲλ12ΪμӴ˴λռƻǿѵٶߵԭ1.2ǰ10ӵλԭÿСʱܶٹ 㡿ʽ̵Ӧã

óϵг̼

Ȼ鲢

𡿽⣺˴Ӽ׵صҵԭƽٶÿxǧף г̣

ãx=0.2ǧ/ӣ

x=0.2гķʽ̵Ľ⣬

...

...

0.260=12

ԭÿСʱ12

22ͼABCDĶԽ߽O㣬DEACCEBD 1֤ıOCEDǾΣ

2AD=5BD=8tanDCEֵ

㡿εжεʣ

1֤ıOCEDƽıΣٸεʿɵACBDõıOCEDǾΣ

2ȸεʿɵOD=BD=4OC=OAAD=CDȻٸݹɶɼDE=OC=3Ǻɵô𰸣 𡿣1֤DEACCEBD ıOCEDƽıΣ ıABCDΣ ACBD DOC=90㣬 ıOCEDǾΣ

2⣺ıABCDΣBD=8 OD=BD=4OC=OAAD=CD AD=5 OC=

=3

ıOCEDǾΣ DE=OC=3

RtDECУsinDCE=

...

=

...

23֪y=k0ͼ󾭹A16 1kֵ

2AֱAC뺯y=ͼڵBxύڵCAB=2BCB꣮

㡿һκĽ⣮

1ɷyTͼ󾭹A16kֵ

2ɣ1Ľۿɵ÷ĽʽȻADOCDBEOCEɵáCEBסCDAεĶӦ߳ɱõB꣮ 𡿽⣺1߷y=k0ͼ󾭹A16 6=

k=6 2k=6

෴ĽʽΪy= ADOCDBEOCE ADBE CEBסCDA

AB=2BC

=

AD=6 BE=2

BΪ1

ߵBڷͼϣ 2= x=3

BΪ32 Bڵڶޣ

...