Consider a quadratic equation $${x^2} - 13x + 36 = 0$$ with coefficients in a base $$b.$$ The solutions of this equation in the same base $$b$$ are $$x=5$$ and $$x=6$$. Then $$b=$$ ______.

$$\mathop {\lim }\limits_{x \to 4} {{\sin \left( {x - 4} \right)} \over {x - 4}} = \_\_\_\_\_\_\_.$$

Let $$f(x)$$ be a polynomial and $$g\left( x \right) = f'\left( x \right)$$ be its derivative. If the degree of $$\left( {f\left( x \right) + f\left( { - x} \right)} \right)$$ is $$10,$$ then the degree of $$\left( {g\left( x \right) - g\left( { - x} \right)} \right)$$ is ___________.

Choose the most appropriate equation for the function drawn as a thick line, in the plot below.