1、 2018 10 120 100 10 3 30 1 x A. 3 1 5 7 xx B. 2 1 10 x x C. x 2 -5=0 D. ) ( b a bx ax 5 2 2 x 2 =6x ( ) A x1=0,x2=-6 B x1=0,x2=6 C x=6 D x=0 3 1 2 2 1 2 x y A 2 1 B -2 1 C 2 -1 D -2 -1 4. 2 2 x x A 1 B 2 C 1 D 2 5. y x 2 3 A. y x 2 3 B. y x 2 3 C. y (x 3) 2D. y (x 3) 26 25 ) 2 ( 4 x x ( ) A 25 2 4 2
2、 x B 0 23 4 2 x C 25 8 4 2 x x D 0 25 8 4 2 x x 7. 2015 2500 2017 3600 2500 1+x =3600 8 ) 2 ( 2 m m x mx y m A 0 2 B 0 C 2 D 9. y 1 4 x 2 AB 12 m ( ) A 3 m B 2 6 m C 4 3 m D 9 m 10 2 2 8 7 0 xx A 3 B 3 C 6 D 9 6 4 24 11 0 5 2 x . 12 x 2 -kx+4 k= 13 x 1 x 2x 2 kx 1 0 k . 14 x 2 -4x-1=0 (x-m) 2 =n , m
3、,n , m+n= . 15 A(2 m) y x 2 A y 16 a b a 2 +2a+b _ 3 6 18 17 x 2 +10x+9=0 18 2 2 ) 2 1 ( ) 3 ( x x 19. 1 2 1 10 3 7 21 20 :x1,x2 x x 2 +(2a-1)x+a 2 =0 (x1+2)(x2+2)=11, a . 21. y=x 2 -4x+7 y=a(x-h) 2 +k 22. 20m 32m 570m 2 3 9 27 23. y=ax+b A B 3 1 y= 3 1 x 2 A B .(1) ;(2) C ABC . 24 20 40 1 2 1 1200
4、2 25 A B C D AB 16 cm AD 6 cm P Q A C P 3 cm/s B B Q 2 cm/s D (1)P Q PBCQ 33 cm 2?(2)P Q P Q 10 cm? x1,x2 x 2 +(2a-1)x+a 2 =0 , x1+x2=1-2a,x1 x2=a 2 , (x1+2)(x2+2)=11, x1x2+2(x1+x2)+4=11, a 2 +2(1-2a)-7=0, a 2 -4a-5=0, a=-1 a=5. =(2a-1) 2 -4a 2 =1-4a 0, a . a=5 , . a=-1. 25. x (40-x)(20+2x)=1200 800
5、+80x-20x-2x 2 -1200=0x 2 -30x+200=0(x-10)(x-20)=0x1=10( ) x2=20 x (40-x)(20+2x)=-2 x 2 +60x+800=-2(x 2 -30x+225)+1250=-2(x-15) 2 +1250 15 1250 24 (1) P Q x s PBCQ 33 cm 2 AP 3x cm CQ 2x cm PB (16 3x)cm. (PB 1 2 33 (16 3x 1 2 33. x 5 P Q 5 s PBCQ 33 cm 2 . (2) P Q a s P Q 10 cm. Q E EB QC EQ BC 6 cm PE |PB BE| |PB QC| |16 3a 2a| |16 5a|(cm) Rt PE 2 EQ 2 PQ 2 (16 5a) 2 6 2 10 2 25a 2 160a 192 0 a1 8 5 a2 24 5 P Q 8 5s 24 5s P Q 10 cm. 22 xm (32-2x)(20-x)=570 640-32x-40x+2x 2 =570 x 2 -36x+35=0 (x-1)(x-35)=0 x1=1 x2=35 1m
