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..123 ax2+bx+c=0 (a0b2-4ac0) ax2+bx+c=0(a0) .

1m x(m1) +5+mx=0.2(m21)x2+(m1)x+1=0m m .3x2-2x-2=0(x+a)2=b .4x2+8x+9=0 ( )A.(x+4)2=7 B.(x+4)2=9 C.(x+4)2=25 D.(x+4)2=7=1 1 =-1 (x1)2=3 D

5(1) 4x216x+15=0 () (2) 9x2=2x26x()(3) (x1)(2x)=1 ()

116/20/200110.1350

216/20/200110.13501500

3RtACBC=90BC=6mAC=8mPQABACBCCP20cm/sQ10cm/sPCQRtACB

4RtACBC=90 AC=6mBC=8mPQABACBCC1m/sPCQRtACB

5(25m)40m(1) 180m2(2) 200m2(3) 250m2(4) (5)

14026(). x .249803698x . ..4980(1x)2=3698

3435

x .41640x( )A.x(x+1)=1640 B. x(x1)=1640 C.2x(x+1)=1640 D.x(x1)=21640B

521x(35010x)20%400

6888cm225cm2

720/40/20 ().AABAB=100.A?.

1

260 .

1 220/200 3110 4 5

x,1350(20010x). (2016+x)((20010x)=1350 x1=11x2=5x=1120010x=2001011=90;x=520010x=200105=1501151350.11905150.

xm(1) x (40-2x) =180 x1=10+ x2=10- ()180m210+ .(2) x (40-2x) =200 x1= x2=10 200m210.(3) x (40-2x) =250 250m2.(4) x (40-2x)=-2(x-10)2+200200 200m2, 10.x (40-3x)=-3(x- )2+ m2, .