I In problems 1 to 7, solve all initial value problems. For each problem, state the interval in which the solution function is defined. 4. (t²+9) y" + 2t y' = 0 y(3) = 2π y'(3) = 2/3 5. y" + y' + 12y = 0 у(л) = −2 y'(л)=-1 6. y" +2y' - 3y = 0 у(2л) = 1 y'(2π) = 1 7. y" +2y'-4y=0 y(2) = 1 y'(0) = −1