新人教版九年级数学第21章一元二次方程教案导学案(全章) - 百度文库 ر

ݷʱ : 2024/12/23 13:53:23һ µȫĶ

3x-23x-5=0 44x2-3x+1=0 ġܽ չ֪ 1ʽƵ̣ 2ùʽһԪη̵һ㲽裺ȷb2-4acֵabcֵ㣮ʽ⣮ 塢ҵ17 5 ѧ˼

7ʱ һԪη̡ʽ2

ѧ ϰ Ŀ ѧϰص ѧϰѵ ʹѧõֵжһԪη̵ĸ ӾĿƳһԪηax2+bx+c=0a0ĨS=b2-4ac Ĺϵ ѧ һѧϰ ֪ ⡿ùʽз̣ݷ̸ʲôۣ 2x2-3x=0 3x2-23x+1=0 4x2+x+1=0 ͼ ʹѧèS=b2-4acֵжһԪη̵ĸ СѧѧwordԾ-ɱ༭

֪̽ ̽д± 2x2-3x=0 3x2-29 0 -15 >0 =0 <0 롿۲ϱϿ֤IJ롣 ǰľ⣬Ѿ֪b2-4ac>0<0=0ǴʽĽǶ ʽx=2x1x2Ĺϵ b2-4acֵ b2-4acķ ȡȻ򲻴ڣ 3x+1=0 4x2+x+1=0 b2-4acķţɳһԪη̵ĸ ѧ˼ĻϷ?b?b?4acb2-4ac>0ʱƽ壬2aۣһԪ2?b?b2?4acٶη̵֪b?4acһһԪһη̵x1=2a?b?b2?4acʶx1=ȵʵb2-4ac=0ʱ?ƽ2a⣬ͬʱϤ?b2b?4ac=0x1=x2=ȵʵb-4ac<0ʱ2a2ƽ壬ûƽûʵ⣮ ۡŵS=b2-4ac>0ʱһԪηax2+bx+c=0a0?һԪη̵ֽⷨʽ䷽һһԪθʵx1=?b?b?4ac?b?b?4acx2= 2a2a22ƵS= b2-4ac=0ʱһԪηax2+bx+c=0a0ʵСѧѧwordԾ-ɱ༭

x1=x2=?b 2a̵ĸǵS=b2-4ac<0ʱһԪηax2+bx+c=0a0?ûʵ ŢֺϳʵҲ b2-4acĹϵ Ӧ ֪ 1̣ⷽж̸ 16x2+8x=-3 9x2+6x+1=0 2x2-9x+8=0 x2-7x-18=0 ̣ⷽжֻb2-4acֵ0С00?зɡb2-4acֵһԪηһʽµóģȱ뽫̻Ϊһʽ 2֪xķx2+(2m+1)x+(m-2)2=0mȡʲôֵʱ ŷȵʵ Ʒȵʵ Ƿûʵ 3xһԪη̣a-2x2-2ax+a+1=0ûʵ⣬ax+3>0Ľ⼯úaʽӱʾ Ҫax+3>0Ľ⼯ax>-3Ľ⼯ôתΪҪжaֵ0ΪһԪη̣a-2x2-2ax+a+1=0ûʵ-2a2-4a-2a+1<0ͿaȡֵΧ ⣺߹xһԪη̣a-2x2-2ax+a+1=0ûʵ ࣨ-2a2-4a-2a+1=4a2-4a2+4a+8<0 a<-2 ax+3>0ax>-3 x<-3 aСѧѧwordԾ-ɱ༭

󲻵ʽĽ⼯Ϊx<-3 aϰ̣ⷽбз̸ 13x2+4x-2=022y2+5=6y 34pp-1-304x-222x-2-80 ġܽ չ֪ S=b2-4ac >0һԪηax2+bx+c=0a0ȵʵ SS=b2-4ac =0һԪηax2+bx+c=0a0ȵʵ SS=b2-4ac <0һԪηax2+bx+c=0a0ûʵӦá 塢ҵ P17 37 ѧ˼ 8ʱ һԪη̡ʽֽⷨ1

1ʹѧʽֽⷨһԪη̵Ļ˼룬ʽֽⷨijѧ ϰ Ŀ 2ʹѧĿľʵһԪ̣Ӷ߷ͽ ѧϰص ѧϰѵ ʽֽⷨһԪη̡ ʽֽⷨһԪη̵Ļ˼롣 ѧ һѧϰ ֪ СѧѧwordԾ-ɱ༭

ЩһԪη̡ ͼ