函數(shù)y=lg[x^2+(k+2)x+5/4]的值域?yàn)橐磺袑?shí)數(shù),k的取值范圍
函數(shù)y=lg[x^2+(k+2)x+5/4]的值域?yàn)橐磺袑?shí)數(shù),k的取值范圍
優(yōu)質(zhì)解答
x²+(k+2)x+5/4>0
因?yàn)槎x域?yàn)橐磺袑?shí)數(shù),開口向上,則用判別式:
△=b^2-4ac是值域?yàn)橐磺袑?shí)數(shù)啊????哦,那反了讓x^2+(k+2)x+5/4只要能取到所有正數(shù)就行了△=b^2-4ac>=0-1=