For string equations with linear density functions, y'' + λ(ax + 1)y = 0, y(-1/2) = y(1/ 2) = 0, and for Sturm-Liouville equations with linear potentials, z''+ (μ-ax)z = 0, z(-1/ 2) = z(1/ 2) = 0, the first eigenvalue λ_1 is a strictly decreasing function of the slope a, the second eigenvalue λ_2, the ratio λ_2/λ_1, the gaps λ_2 -λ_1 andμ_2-μ_1 between the first two eigenvalues of these two equations are strictly increasing functions of the slope a for 0 ≤ a ≤ 2.