二次函數(shù)交點(diǎn)式y(tǒng)=a(x-x1)(x-x2)和y=a(x+x1)(x+x2)怎么回事?

數(shù)學(xué)人氣：962 ℃時(shí)間：2020-03-27 20:24:53

優(yōu)質(zhì)解答

y=a(x-x1)(x-x2)與x軸的交點(diǎn)是:(x1,0);(x2,0)
y=a(x+x1)(x+x2)與x軸的交點(diǎn)是:(-x1,0);(-x2,0)他們一樣嗎？不一樣。交點(diǎn)的橫坐標(biāo)分別是相反數(shù)一般交點(diǎn)式是：y=a(x-x1)(x-x2)算出來(lái)的結(jié)果不一樣？不一樣。令二次函數(shù)與x軸的交點(diǎn)橫坐標(biāo)分別是x1,x2則可設(shè)交點(diǎn)式為：y=a(x-x1)(x-x2)而不能設(shè)交點(diǎn)式為：y=a(x+x1)(x+x2)什么時(shí)候用y=a(x+x1)(x+x2？在二次函數(shù)與x軸的交點(diǎn)橫坐標(biāo)分別是-x1,-x2時(shí)用：y=a(x+x1)(x+x2)