In Problems 1 through 16, a homogeneous second-order linear differential equation, two functions y₁ and y₂, and a pair of initial conditions are given. First verify that y₁ and y₂ are solutions of the differential equation. Then find a particular solution of the form y = c₁y₁ + c₂y₂ that satisfies the given initial conditions. Primes denote derivatives with respect to x.

y" + 4y = 0; y₁ = cos 2x, y₂ = sin 2x; y(0) = 3, y' (0) = 8