1.$\displaystyle lim_{x\rightarrow-5}\frac{x^3+125}{(-5-x)^3}$

I reduced it to:

$\displaystyle lim_{x\rightarrow-5}\frac{x^{2}+5x+25}{x^{2}+10x+25}$

But I don't know what to do after that.

2.Find equations of all tangent lines to the graph of $\displaystyle y=4x^{3}+5x-8$

I took the derivative of the equation, which was:

$\displaystyle \acute{y}=12x^{2}+5$

I then thought I might need to make the derivative equal to the original equation, so:

$\displaystyle 12x^{2}+5=4x^{3}+5x-8$

But I don't really know...

3.Determine values of constant real numbers a, b so that the function:

$\displaystyle f(x)= ax^{2}-8x+6$ if $\displaystyle x\leq-1$

$\displaystyle f(x)= bx+2$ if x is greater than -1

is differentiable at x=-1.

No idea how to do this one.