對(duì)于區(qū)間[a,b],若函數(shù)y=f(x)同時(shí)滿足下列兩個(gè)條件：1.函數(shù)y=f(x)在[a,b]上是單調(diào)函數(shù)；2.函數(shù)y=f(x) ,x∈[
對(duì)于區(qū)間[a,b],若函數(shù)y=f(x)同時(shí)滿足下列兩個(gè)條件：1.函數(shù)y=f(x)在[a,b]上是單調(diào)函數(shù)；2.函數(shù)y=f(x) ,x∈[a,b]的值域是[a,b]為函數(shù)y=f(x)的保值區(qū)間。函數(shù)y=x^2+m(m≠0)是否存在保值區(qū)間？若存在，求出相應(yīng)的實(shí)數(shù)m的取值范圍；若不存在，試說(shuō)明理由