Alan

Use the same method as was given here:  https://web2.0calc.com/questions/graphing_51126#r2

As follows:

This should help:

Use the cosine rule.

Like so:

This should help:

For f(5x+5) to equal 4 we must have 5x+5 = 3,  so x = -2/5.

At x = -2/5 we have y = 1/5 * 4 - 5  or y = -21/5 

So the point (-2/5, -21/5) is on the graph.   (The point can also be expressed as (-0.4, -4.2) )

A cubic polynomial has three roots.  A quartic polynomial has four.

This should help (it uses the chain rule):

All the sides of a triangle have integer length. The perimeter of the triangle is 50 and the triangle is isosceles. How many such non-congruent triangles are there?

Let s be the length of two of the sides and b be the length of the third side.

We must have $50=2s+b$ and $b<2s$

Try values of s from 1 upwards until the second expression above is violated, remembering that b must be an integer.