element: 8 + y^3 8 + y^3 = 2^3 + y^3 we are waiting to element the above expression by means of utilizing the sum of a cube formula: a^3 + b^3 = (a + b)(a^2 - ab + b^2) 8 = 2 * 2 * 2 (for this reason 2 is a cube of 8) y = y * y * y (for this reason y is a cube of y^3) for this reason the respond is: (2 + y)(4 - 2y + y^2) or (y +2)(y^2 - 2y + 4)
The first reply gave you a formula for the difference of two cubes.
A^3 - B^3 = (A - B)(A^2 + AB + B^2)
I will use that formula.
We need to have the SAME POWER.
So, 27 can be written as 3^3.
Also, 8a^3 can be written as 2^3(a^3) becoming 2a.
Do you see that we now have the same power or exponent of 3?
In the formula A = 2a and B = 3.
We now plug and chug.
A^3 - B^3 = (A - B)(A^2 + AB + B^2)
(2^3a^3 - 3^3) = (2a - 3)(4a^2 + 6a + 9)
The final answer is (2a - 3)(4a^2 + 6a + 9).
NOTE: If you multiply (2a - 3) by (4a^2 + 6a + 9), you'll end up with the original difference of cubes given. This is how you can check to see if the math work is correct. Why not try it?