Math(please check)
posted by Hannah on .
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?

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. 
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?