2020年中考数学压轴题热点专练附解答：一元二次方程及应用

22222222热点专题

一元二次方及应用【点】元次程根求问【例12019xx+ax0a+4bA2

B31D6Ax1+ax+21+b01bb21A【变式1-12019ax2+0x0aA0D

B11D2222222222222222222222122222222222222222222222122+a10xa10a10aaD:【变式1-220192kx+0x1kA1

B011DAx1k+kk1A:【点】方解元次程【例2+8+90A+49

B+4C+4DD+8x0+8x+8x+167x+47D:【变式2-12019

xA

B146Ax0＝17A:【点】式解解元次程【例3x3x2121222222121212122121222222121212122xx3x2x2:【变式3-1ababam+2m[m+2+m3][m+2]24

m1070m3m:【变式3-220192xx1xx2xx220x0x2x10x2x1x2x1:【点】元次程判式题【例42019xa40

022221222221121222212222211212222121212164aaaaa0:【变式4-12019xk0k

x

xk0

3k0k

k

:eq\o\ac(△,)eq\o\ac(△,)【变式4-22019

64m+10mxx4x+4m+1044m+102xx+1x+6xx+1x+x16:eq\o\ac(△,)x【点】元次程根系的系题2212122121221212212122122121212212212【例5x+2a+5x1212xxxa(1)a(2)0xa+506﹣02ax+xxx+x

3xx30363aa

aa101:k【变式5-12019kxx+1kxx+xx4(1)kk03+10x

kk4k10k

212121212121212121212212k

2x+10x+

x

x++xx

k1kk:k0+x+x4k【点】元次程增率题【例620182420020162019(1)2016201810%201920162018x1+24200x10%x2016201810%2242001+10%26620201926620:【变式6-1201920162500360021222212221222212220194200(1)20162018201942001+3600x20%x201620182420020194200:【点】元次程面问【例720190cmcm20030x20x[302x+x]x200xx+50x

xx2200cm

:2122121221【变式7-1201916ABBx112x1x169x16x:【点】元次程销问【例8201923200032000[200][300+5200]xx2122222221222222【变式8-160yxyx209020909kx+bx2x4140

y+100260xx10+90x1x9x2090:2019x4A

1

B5C+2

3D

3D22222222222222xx0x41x4x3D:2019x

A

B

k

CDk0k

1+3k0kk

k0k

:20192xx0A8

B989D12Bxx6+364kk32+3k22222222222xx6+4k0kx2+2k9B:abxxx0mA34

BD3036A8ax12++2b12bb4ax12++2a12aabax12++2122a2a6m+236m34222222121212112112122222221212121121121212112122122121212A:•kx+++0AC

BDAykxk0k40A:ax00b4002019x3xx+3x+xx2A10

B98DDx3+10xx+10xxxxx2x+xx+xxx+x3x1xxx27D:ax0+x

x

20192122222222222122222222224A4

B56D+43x76:2019xAC

x1BDA﹣15A:ax00b40002019xxx+0cA4

B21DAx+4cc0c4A:c10a2x

x+4a

a222222122221222222212222122xx+4244a8:11.2019x1+xx+20x

1x:xkxkkk0kkkkk1:6048.610%x＝48.6x10%x1.92212年数12222212221222112212年数1222221222122211110%:ax1xb520%1+7.2x20%x20%:1+12+316x

x

xx340x

x17x

x

x

x

x

x

:2a1+aa20x1a2x+xx16a22222121221212222212122121221122212212a1xaa[2a]a20aa22x+a1xaxxxx+xx[21]aa2a6aa1:1720190167.25.6%20181+7.2xx2.227.220%0.44

100%10%10%:1221221221225040m306420003xmx2x240x30x30x90x60，:2.421+