As x approaches either positive or negative infinity, y will approach positive infinity.
This is because x^2 will grow large much quicker than b*x, so it has more importance. So when considering the limit, we can imagine that the equation looks like this:
y = x^2
This equation will go to infinity for x approaching both negative and positive infinity.
Sin2x = 2 sinx cosx
so 12 sinx cosx = 6 sin2x Answer
