∵方程2x2+3x-1=0的兩根為x

1、x2

∴由根與系數(shù)關(guān)系得

x1+x2=-3/2 ①

x1x2=-1/2 ②

∵1/x1+1/x2=(x1+x2)/ x1x2 ③

∴將①②代入③得

1/x1+1/x2=(x1+x2)/ x1x2 =(-3/2 )/(-1/2 )=3

1.初中數(shù)學(xué)《二元一次方程與一次函數(shù)》課例中

解：1.利用韋達(dá)定理x1+x2=-b/a=-2/3.x1*x2=c/a=-1/2 同時(shí)利用恒等式：|x1-x2|=根號(hào)[（x1+x2）^2-4x1x2] 2.利用兩個(gè)關(guān)于k的不等式：①德?tīng)査?b^2-4ac>0 ②|x1-x2|=根號(hào)[（x1+x2）^2-4x1x2]

我今年暑假被預(yù)約去一個(gè)補(bǔ)習(xí)學(xué)校教初中文言文,請(qǐng)問(wèn)

宜州區(qū)附近初二家教語(yǔ)文戴氏教育1對(duì)1

初二數(shù)學(xué)分式乘法:已知r=100,求2r+2/r2+2r+1+r，1

2.一直從事初中物理教學(xué),但是中學(xué)一級(jí)教師職稱

x1-x2=[√（b^2-4ac）]/a=1/2

利用求根公式

初二數(shù)學(xué)急救！快！有兩個(gè)課外小組的同學(xué)到郊外植物標(biāo)本

Every family has its own rules. My family is same as others. Firstly, as the only child at home, I am not allowed to come home later than eight at night. Secondly, I have to go to bed before night p.m. everyday. Thirdly, I need to be polite to my parents and other family members. There are not only rules for me but also rules for my parents. My parents are not allowed to beat their child, which is me. These are all the rules in my family. I love my family

原創(chuàng)，放心使用~

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