What is the smallest value o fm for which f(x) =`x^(2)+mx+5` is increasing in the interval `1 lex le 2` ?

Options

A. m = 0
B. m= -1
C. m = -2
D. m = -3

Answer

C

Explanation

f(x) `=x^(2)+mx+5`
consider option (c ) m =-2
f(x) `=x^(2)-2x+5 rarr f(x)=2x-2`
It is clear that `f(x) gt0` in interval `1 le x le 2`
`therfore m=-2`