Alan

Here's how to do it:

Area = (1/2)*base*height

14 = (1/2)*(h + 3)*h     where h is the height

Multiply both sides by 2 and expand the bracketed term

28 = h^2 + 3h

Subtract 28 from both sides

h^2 + 3h - 28 = 0

This factors as (h + 7)(h - 4) = 0

So the height is either -7 or +4.  Since you don't want a negative height then height = 4 cm (so base = 4+3 = 7 cm.

This means you have  n^2 - n = 72

Rewrite as  n^2 - n - 72 = 0

This can be factored as (n + 8)(n - 9) = 0

The two possible mathematical solutions are n = 9 and n = -8.  Hpowever, you can't have a negative number of teams, so the only practical solution is n = 9 teams.

1.  If vector B is has magnitude 140km and is 65° above the positive x axis then -B will have the same magnitude but will be 65° below the negative x axis (assuming the vector starts at (0, 0).  i.e. both the x and y coordinates will be reversed.

2.  65° East of North is 25° above the positive x-axis!

Or write it in the form

 \(r_1e^{i\theta_1}/r_2e^{i\theta_2}\rightarrow r_1e^{i\theta_1}\times \frac{1}{r_2}e^{-i\theta_2}\rightarrow \frac{r_1}{r_2}e^{i(\theta_1-\theta_2)}\)

Edited to correct the magnitudes.

The equation of a straight line can be written as f(x) = m*x + c where m and c are constants found from the given information as follows:

 f(-4) = 21  so  21 = -4*m + c    ...(1)

 f(4)  = -3  so   -3 = 4*m + c     ...(2)

Add (1) and (2) term by term to get  21 - 3 = -4m + 4m + c + c  or 18 = 2c so c = 9

Put this back into (2) to get  -3 = 4m + 9   so 4m = -12  so m = -3

Hence the straight line function is  f(x) = -3x + 9

Now simply replace x by 9 to work out what f(9) is.

There is no statistics button on the calculator here.

Very nicely done heureka!

This is unknown (as I suspect you already knew!).

See https://en.wikipedia.org/wiki/Euclid%E2%80%93Mullin_sequence 

Do you mean something like y = a*ln(x) + b ?

If so then x = e^(y-b)/a