2014年浙江省嘉兴市中考三模考试数学试题2014.5.28(2)

18．(a 2b)(a 2b)

1

b(a 8b) 2

a2 4b2 a2

1

·························································································· 6分 ab 4b2 ·

2

1

············································································································· 8分 ab ·

2

19．设 A x（度），则 B x 20， C 2x．

根据四边形内角和定理得，x (x 20) 2x 60 360． ········································ 4分 解得，x 70．

∴ A 70 ， B 90 ， C 140 ． ····································································· 8分

20．（1）B机器的产量为150件， ·················································································· 2分

A机器的产量约为210件． ·············································································· 4分

（2）C机器产量的百分比为40%． ················································································ 6分

设C机器的产量为x， 由

150x

，得x 240，即C机器的产量为240件． ···································· 8分

25%40%

21．（1）∵AE⊥BC，AF⊥CD，∴∠AEB=∠AFD=90°． ·············································· 2分 ∵四边形ABCD是平行四边形，∴∠ABE=∠ADF． ···················································· 4分 ∴△ABE∽△ADF ···································································································· 5分 （2）∵△ABE∽△ADF， ∴∠BAG=∠DAH．

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