Find kkk such that x2+kx+1=0x^2 + kx + 1 = 0x2+kx+1=0 has at least one root in (0,1)(0, 1)(0,1).
k<−2k < -2k<−2
k>−2k > -2k>−2
k<−2k < -2k<−2 or k>−2k > -2k>−2 is not the only condition. f(0)f(1)<0f(0)f(1) < 0f(0)f(1)<0 or vertex condition.
k<−2.5k < -2.5k<−2.5