Question

已知函数f(x)=x^2+mx+m-1

1,若函数y=lg[f(x)]在区间[2,4]上有意义，求实数m取值范围
2，若函数y=|f(x)|在区间[2,4]上单调递增，求实数m取值范围
在线等，拜托拜托详细过程~~

Answer 1

1.f(2) = 3(m+1)
f(4) = 5m+15
f(2) > 0, 3m + 3 > 0, m > -1
f(4) > 0, m > -3
1. therefore m > -1 is required
2. f(2) = 3(m+1), |f(2)| = 3(m+1) if m > -1, or 3(1-m) if m < -1
when m < -1 |f(x)| 递减
therefore, m>-1 guarantees |f(x)| 递增