Playing with Cubes Today…..
With the given bag of cubes,
 Build a large cube and a small cube
 Let the length of each side of the larger cube be
x and the
length of the smaller cube be y.
[STOP]
Volume of larger cube =
x3
Volume of smaller cube = 3
y by the smaller cube to form 1
 Replace part of the larger cube
large cube with 2 colours.
Express algebraically in terms of x and y , the volume of the
large cube that you have just formed.
Example, x 3  _____+_____+_____+______
Hey, this is the result…..
x 3  y 3  x 2  x  y   xy  x  y   y 2  x  y 
x 3  y 3   x  y   x 2  xy  y 2 
How do you derive the sum of two
3
3
x

y
cubes?
x3  y 3  y 3  y 3  x 2  x  y   xy  x  y   y 2  x  y 
 2 y 3  x 3  x 2 y  x 2 y  xy 2  xy 2  y 3
 x  x y  x y  xy  xy  y
3
 x  x y  x y  xy  xy  y
3
3
3
2
2
2
2
2
2
2
2
 x 2  x  y   xy  x  y   y 2  x  y 
x 3  y 3   x  y   x 2  xy  y 2 
x 3  y 3   x  y   x 2  xy  y 2 
x  y   x  y   x  xy  y
3
3
SAME ,
2
2

DIFFERENT , PLUS