what are the values of: {1\over a}+ {1\over b }+ {1\over c} (think of fractions),
{1\over ab}+ {1\over bc }+ {1\over ca}
and a^2 +b^2 + c^2?
In the diagram the coloured squares have sides of length a, b
and c. Use the areas in the diagram to write down a formula for
the expansion of (a + b + c)^2 and explain your method.
Using your expansion of (a + b + c)^2 to help you, expand (a + b
+ c)^3. Can you explain each term of the expansion using a diagram
of a cube where each face has been cut up in a similar way to the
square above?