Y' = (e^(3x+15x^2))' = e^(3x+15x^2)* (3x+15x^2)' = e^(3x+15x^2)*(3+30x)
y' = (e^3x)' * cos^2 (5x) + e^3x * (cos^2 5x)' = e^3x * (3x)' * cos^2 5x + e^3x * 2cos5x * (cos5x)' = 3*e^3x *cos^2 5x + 2*e^3x * cos5x * (-sin5x) * (5x)' = 3*e^3x *cos^2 5x - 2*e^3x * cos5x * sin5x * 5