Posted by Hannah on Sunday, August 29, 2010 at 12:01am.
Simplify each expression:
1) (x+8)^2 = x^2 + 64
2) (x2)^3 = x^3  8
3) (x2y)(x+y) = x^2  xy 2y^2
4) (x+2)(x^2+3x2) = x^3 + 5x^2 + 4x4
Are my answers correct?

Math(please check)  MathMate, Sunday, August 29, 2010 at 8:59am
Numbers 3) and 4) are correct.
For numbers 1) and 2), you have missed out terms, probably you have not used the right standard formulae.
(a+b)² = a² + 2ab + b²
(ab)² = a²  2ab + b²
(a+b)³ = a³ + 3a²b + 3ab² + b³
(ab)³ = a³  3a²b + 3ab²  b³
If you are in an examination where you do not have an easy way to double check the standard formulae, you can treat
(a+b)² = (a+b)(a+b)
which you seem to have no problem solving. 
Math(please check)  Hannah, Sunday, August 29, 2010 at 6:11pm
so for (x+8)^2 i would use
a^2 + 2ab + b^2 and a would be 8 but what is b? Would it be 64?