For which value of a the system of ODEs ỷ₁ = sinh(y₁) + a tanh(y₂), y₂ = −2 cos(y₁) + 2e³¹+½ + tanh(y₂), linearised around (y₁, y₂) = (0,0) displays an unstable focus? Select one: a. −1/2 < a < 0 O b. a = 2 O c. 0 < a <2 O d. a < -1/2

Consider the differential equation y'= 1- y.

List the values for L such that the function y = cos(Lx) is a nontrivial solution for the ODE 4y + y = 0. 2,-2 O 2,0 O 0,-2 2,0,-2